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Abstract
Haemangiopericytoma (HPC) was described in 1942 by Stout and Murray as a distinctive soft tissue neoplasm, presumably of pericytic origin, exhibiting a characteristic well-developed "staghorn" branching vascular pattern. Over the years, it appeared that this growth pattern was a non-specific one, shared by numerous, unrelated benign and malignant lesions, and that HPC was better considered as a diagnosis of exclusion. Three categories of lesion may now be individualized within the heterogeneous group of HPC-like neoplasms. The first category corresponds to those non-HPC neoplasms that occasionally display HPC-like features (e.g. synovial sarcoma). Lesions belonging to the second category show clear evidence of myoid/pericytic differentiation and correspond to true HPCs. They generally show a benign clinical course, and include glomangiopericytoma/myopericytoma, infantile myofibromatosis (previously called infantile HPC), and a subset of sinonasal HPCs. The third category is the solitary fibrous tumour (SFT) lesional group, which includes fibrous-to-cellular SFTs, and related lesions such as giant cell angiofibromas and lipomatous HPCs. In practice, any HPC-like lesion can be allocated to one of these categories, leaving the ill-defined "haemangiopericytoma" category empty.
... A rare mesenchymal neoplasm of fibroblastic differentiation, solitary fibrous tumors (SFT) may arise anywhere in the body. 1 Initially, SFTs were identified as cellular tumors with numerous branching or "staghorn" vessels, a description that was used to characterize the unclear entity known as hemangiopericytoma (HPC). 1 In the 2016 World Health Organization (WHO) classification of central nervous system (CNS) tumors, SFT and HPC were combined under one category due to the shared presence of the NAB2::STAT6 fusion gene; however, in the latest 2021 WHO CNS classification, they are now recognized simply as SFTs and graded according to their histological features. About 5% of SFT cases have a poor clinical course with local recurrence or distant metastasis; nevertheless, the majority of cases are pathologically benign and show a favorable clinical course. 2 It was previously challenging to establish which tumors would act aggressively. ...
... A rare mesenchymal neoplasm of fibroblastic differentiation, solitary fibrous tumors (SFT) may arise anywhere in the body. 1 Initially, SFTs were identified as cellular tumors with numerous branching or "staghorn" vessels, a description that was used to characterize the unclear entity known as hemangiopericytoma (HPC). 1 In the 2016 World Health Organization (WHO) classification of central nervous system (CNS) tumors, SFT and HPC were combined under one category due to the shared presence of the NAB2::STAT6 fusion gene; however, in the latest 2021 WHO CNS classification, they are now recognized simply as SFTs and graded according to their histological features. About 5% of SFT cases have a poor clinical course with local recurrence or distant metastasis; nevertheless, the majority of cases are pathologically benign and show a favorable clinical course. 2 It was previously challenging to establish which tumors would act aggressively. ...
... Less than three mitoses are typically found in every 10 high-power fields. 1 Regarding immunohistochemistry, Bcl-2, CD99, and CD34 are acknowledged as helpful favorable indicators for traditional SFTs/HPCs. Han et al. investigated immunochemical detection in 53 instances of SFTs/ HPCs and found that 47/53 cases (88.7%), 50/53 cases (94.3%), and 51/53 cases (96.2%) had positive results for CD34, CD99, and Bcl-2, respectively. ...
This report details a rare case of a 30-year-old female presenting with neurological symptoms, including headaches , seizures, and left-sided weakness. Imaging revealed a mass in the right parafalcine region of her brain. Surgical resection identified a tumor with two distinct components. The first component exhibited characteristics of a classic solitary fibrous tumor (SFT) with typical fibroblastic cells and branching blood vessels. The second component showed high-grade sarcoma with chondrosarcomatous differentiation , a rare feature in SFT. Immunohistochemistry confirmed dedifferentiation with decreased STAT6 expression in the sarcomatous areas compared to the conventional SFT. This case highlights the challenges of managing dedifferentiated SFTs, especially in the brain, where surgical limitations increase risks. Despite the rarity of this presentation , it emphasizes the importance of recognizing this variant for appropriate diagnosis and management.
... The macroscopical appearance is of a solid mass, firmly elastic at the edge with a smooth, thick white-yellow capsule [104]; in the context of the lesion necrosis, hemorrhage as well as areas of cystic necrosis and myxoid degeneration [106] can be observed. Initially, STFLs were described as hemangiopericytomas (HPCs), soft tissue neoplasms with a characteristically branched vascular pattern, a feature later understood to be non-specific and shared among many neoplasms [107]. These lesions do not have a microscopical unequivocal appearance, ranging from more to less fibrous tumors. ...
... Gengler et al proposed a classification system that account for this difference; they further identified a cellular and a fibrous type of solitary fibrous tumor [107]. Cells with a spindle-like appearance and ovoid, banded, or fusiform nuclei are interspersed in a "pattern-less" pattern in a hyaline-radiated area [104,108]. ...
... Cells with a spindle-like appearance and ovoid, banded, or fusiform nuclei are interspersed in a "pattern-less" pattern in a hyaline-radiated area [104,108]. Other notable features include a myxoid stroma and branching vessels with thick walls, leading to its previous classification as an HPC [104,107]. Known malignancy predictors are nuclear atypia, areas of necrosis, and a high rate of mitotic figures [109]. Immunohistochemistry is a tool of utmost importance in correctly diagnosing an SFTL, and stains are positive for the following proteins: CD34, expressed in endothelial and mesenchymal cells [108]; CD99; BCL-2; and vimentin [110]. ...
It is important to be familiar with the typical imaging features of the uncommon or even extremely rare focal liver lesions (FLL). Current guidelines of the World Federation for Ultrasound in Medicine and Biology (WFUMB) is aimed at assessing the usefulness of contrast enhanced ultrasound (CEUS) in the management of various FLL. In this review, we aim to summarize the ultrasound and CEUS characteristics with literature review of some extremely rare benign FLL, which might be helpful for improving diagnostic efficiency clinically
... Con la tinción de hematoxilina y eosina, los tumores fibrosos solitarios se caracterizan por presentar un gran rango de características morfológicas; varían desde aquellos predominantemente fibrosos, que contienen grandes áreas de fibras de colágeno y vasos sanguíneos de paredes gruesas y hialinas, hasta tumores menos fibrosos y con mayor contenido celular 10,38 . Habitualmente, se caracterizan por áreas radiadas hipocelulares o acelulares hialinas ricas en colágeno, que alternan con áreas pobladas por células fusiformes y ovoideas, con núcleos elongados que se distribuyen desordenadamente 2,7,8,10,11,17,20,23,25,35 . ...
... Otra característica de los tumores fibrosos solitarios del hígado es un patrón vascular "enmarañado" con numerosos vasos de paredes gruesas, por lo cual estos tumores se clasificaron en la antigüedad como hemangiopericitomas 8,11,25,37,38 . En un elegante artículo, Gengler y Guillou describieron dos tipos de presentación histológica básica en los tumores fibrosos solitarios: una forma fibrosa y otra celular (tabla 2) 38 . ...
... La característica inmunohistoquímica básica de los tumores fibrosos solitarios del hígado, es la expresión de CD34, CD99, Bcl-2 y vimentina 7,8,[10][11][12][13][14][15][16][17][18]20,[23][24][25][26][27]29,35,[37][38][39][40] . El CD34 es un antígeno de células progenitoras mieloides, que también se manifiesta en células endoteliales y en células mesenquimales, incluyendo algunos subtipos de fibroblastos 2 . ...
El tumor fibroso solitario del hígado es infrecuente. Hasta la fecha, se han reportado menos de 50 casos en la literatura científica inglesa, la mayoría de los cuales se comportaron como tumores benignos. El objetivo del presente artículo es actualizar el conocimiento sobre este tumor porque, debido a su rareza, la presentación clínica, el estudio, el tratamiento y el pronóstico no son bien conocidos. Habitualmente, no produce sintomatología o es inespecífica y su comportamiento a largo plazo es incierto; no obstante, en algunos casos, se comporta agresivamente como un sarcoma de mal pronóstico. Actualmente, solo el tratamiento quirúrgico puede ofrecer una oportunidad terapéutica para estos pacientes. Debido a la falta de conocimiento sobre el comportamiento a largo plazo de estos tumores supuestamente benignos y a la falta de tratamiento médico específico, se sugiere el seguimiento metódico a largo plazo para garantizar la supervivencia de los pacientes operados por un tumor fibroso solitario del hígado.
... Solitary fibrous tumors (SFT) are rare mesenchymal neoplasms of fibroblastic origin that can develop in any part of the body, described for the first time by Klemperer et al. way back in 1931 [1]. SFT were initially recognized as cellular neoplasms featuring numerous branching, "staghorn" vessels, a description that was also used to define the poorly understood entity known as hemangiopericytoma (HPC) [2]. They have been reported in various anatomic locations, with the pleura being the most common site [1]. ...
... The histopathological features of conventional SFT/HPC typically include irregularly distributed hyalinized collagen bundles, thin-walled blood vessels with a characteristic staghorn-like appearance, and monomorphic hypercellular spindle cells with round or oval nuclei. Mitoses are generally rare, with fewer than three per ten high-power fields [2]. Immunohistochemically, Bcl-2, CD99, and CD34 are recognized as favourable markers for conventional SFT/HPC. ...
Introduction and Importance
Solitary fibrous tumors (SFTs) are rare mesenchymal neoplasms, initially described in the pleura but capable of arising in various anatomical locations, including the central nervous system. Dedifferentiation, characterized by the transformation of a low-grade tumor into a high-grade sarcoma, is an uncommon phenomenon in SFTs, especially in the intracranial region.
Case presentation
A 31-year-old male visited the neurology outpatient department with complaints of frequent headaches, seizures, speech difficulties, and weakness on the left side of his body. MRI was done which showed a relatively well defined T1 isointense and T2 hypointense extra-axial mass lesion in the right frontal lobe. Histopathological analysis confirmed the diagnosis of dedifferentiated SFT, marked by distinct fibroblastic differentiation and areas of high-grade sarcomatous transformation (rhabdomyosarcoma). Immunohistochemically, areas with fibroblastic differentiation showed strong and diffuse positivity for CD99, STAT6, vimentin and focal BCL-2 High-grade sarcomatous area was positive for vimentin, desmin and Myo-D1 and was negative for GFAP, EMA, PR, S-100, SMA and CD-34. It also showed focal positivity for STAT-6. The final diagnosis of intracranial solitary fibrous tumor with rhabdomyosarcomatous differentiation was made. At 2 months of follow-up, the patient is doing well.
Clinical discussion
Given the rarity of dedifferentiation in intracranial SFTs, there is limited consensus on optimal management strategies. En bloc resection remains the primary treatment approach, though the unpredictable behaviour of dedifferentiated SFTs complicates prognosis. This case underscores the importance of integrating clinical, radiological, and pathological findings for accurate diagnosis and discusses the need for further research into effective therapeutic options for dedifferentiated SFTs, particularly in challenging intracranial cases.
Conclusion
This case report presents a unique instance of an intracranial dedifferentiated SFT with rhabdomyosarcomatous dedifferentiation, highlighting the significant diagnostic challenges posed by this rare entity.
... The term "hemangiopericytoma" (HPC) was used to refer to tumors with a pericytic origin that exhibited similar features to SFT [3,4]. However, as increasing evidence of clinicopathological similarities accumulated, these two tumor types were eventually recognized as a single entity [5][6][7]. SFT is categorized as a fibroblastic neoplasm with differentiation between central nervous system (CNS) and non-CNS SFTs in the WHO classification of Soft Tissue and Bone Tumors [8,9]. Nevertheless, recognizing that histological features alone may not adequately reflect clinical behavior, there is a growing emphasis on updated risk stratification models as essential complements to SFT classification [10,11]. ...
... In the beginning, SFT was considered a low-grade tumor, whereas HPC displayed a more aggressive pattern. However, as mounting evidence of these similarities was confirmed, merging these two entities into a single category gained support among researchers [5][6][7]. In the current WHO Classification, the term "hemangiopericytoma" was removed, and the relationship between SFT and HPC has been revised, recognizing them as different manifestations of the same disease entity [8,9]. ...
Solitary fibrous tumor (SFT) is a rare fibroblastic mesenchymal neoplasm. The current classification has merged SFT and hemangiopericytoma (HPC) into the same tumor entity, while the risk stratification models have been developed to compensate for clinical prediction. Typically, slow-growing and asymptomatic, SFT can occur in various anatomical sites, most commonly in the pleura. Histologically, SFT consists of spindle to oval cells with minimal patterned growth, surrounded by stromal collagen and unique vascular patterns. Molecularly, SFT is defined by the fusion of NGFI-A-binding protein 2 (NAB2) and signal transducer and activator of transcription 6 (STAT6) genes as NAB2-STAT6. This fusion transforms NAB2 into a transcriptional activator, activating early growth response 1 (EGR1) and contributing to SFT pathogenesis and development. There are several fusion variants of NAB2-STAT6 in tumor tissues, with the most frequent ones being NAB2ex4-STAT6ex2 and NAB2ex6-STAT6ex16/ex17. Diagnostic methods play a crucial role in SFT clinical practice and basic research, including RT-PCR, next-generation sequencing (NGS), FISH, immunohistochemistry (IHC), and Western blot analysis, each with distinct capabilities and limitations. Traditional treatment strategies of SFT encompass surgical resection, radiation therapy, and chemotherapy, while emerging management regimes include antiangiogenic agents, immunotherapy, RNA-targeting technologies, and potential targeted drugs. This review provides an update on SFT's clinical and molecular aspects, diagnostic methods, and potential therapies.
... A post-operative brain CT scan, conducted without contrast injection, depicted the resection of the sellar and suprasellar mass, along with the implantation of abdominal subcutaneous fat tissue. While the precise origin of SFT or HPC remains uncertain, there is consensus on its mesenchymal nature characterized by HPC-like features, such as a monotonous cell population, varying cellularity, and the presence of branching blood vessels (16). Ultrastructurally, both SFT and HPC exhibit diverse degrees of pericytic, fibroblastic, or myofibroblastic differentiation. ...
... Ultrastructurally, both SFT and HPC exhibit diverse degrees of pericytic, fibroblastic, or myofibroblastic differentiation. Gengler and Guillou clarified that, excluding myopericytoma, infantile myopericytosis, and HPC of the sinonasal tract, all HPCs lacking pericytic differentiation are considered variants of SFT, resembling a cellular form of SFT within a morphological continuum (16). Tumors characterized by lower cellularity and high collagen content are designated as grade I (formerly SFT), whereas those with increased cellularity, reduced collagen, and characteristic staghorn vasculature are categorized as grade II (formerly HPC). ...
Hemangiopericytoma (HPC) constitutes less than 1% of all primary central nervous system tumors. It is a vascular neoplasm with potential malignancy that, in rare instances, manifests as a primary lesion within the brain. Typically, it originates from the meninges. Here, we describe an exceptionally uncommon sellar region solitary fibrous tumor/hemangiopericytoma (SFT/HPC) that mimicked a nonfunctional pituitary adenoma.
Introduction and importance
Case presentation
A 54-year-old male was referred to our hospital due to progressive blurred vision in the left eye over the past year. A homogeneous iso-dense extra-axial intrasellar round mass with extension into the suprasellar region, mainly on the left side, along with bony erosion and osteolysis around the sellar region, was observed on a brain computed tomography (CT) scan. Brain magnetic resonance imaging (MRI) revealed a well-defined 251,713 mm mass with iso-signal on T1-weighted images and hypersignal on T2-weighted images, originating from the pituitary gland within the sella turcica. The mass avidly enhanced following Gadolinium injection and adhered to both carotid arteries without vascular compression or invasion. It extended to the suprasellar cistern and compressed the optic chiasm. The diagnosis was nonfunctional pituitary macroadenoma, leading to the decision for Endoscopic Trans-Sphenoidal Surgery (ETSS). A non-sustainable, soft, grayish mass was grossly and totally resected during the operation. Subsequently, there was a significant improvement in visual acuity during the early postoperative period. Histopathologic examination confirmed hemangiopericytoma (WHO grade II).
Conclusion
Due to its malignant nature, hemangiopericytoma should be included in the differential diagnosis of a sellar mass, both from a clinical and morphological perspective.
... Solitary fibrous tumors (SFTs) are rare mesenchymal tumors with an estimated incidence rate of 1 in 1 million people per year (3,4). They can develop in any location in the body, but most commonly arise in pleural, dural, or pelvic soft tissues. ...
... Immunohistochemistry using antibodies targeting the C-terminus of STAT6 reveals strong nuclear staining in the presence of the chimeric protein NAB2-STAT6, leading to STAT6 nuclear staining as a diagnostic tool for SFTs (8). Hemangiopericytomas were previously diagnosed as a distinct soft tissue neoplasm and upon discovery of the NAB2-STAT6 gene fusion, are now classified as SFTs (3,4).Despite the introduction of molecular diagnostic tools, many SFTs are still misdiagnosed or misclassified, owing to our fundamental lack of understanding of their etiology. ...
The pathogenesis of many rare tumor types is poorly understood, preventing the design of effective treatments. Solitary fibrous tumors (SFTs) are neoplasms of mesenchymal origin that affect 1/1,000,000 individuals every year and are clinically assimilated to soft tissue sarcomas. SFTs can arise throughout the body and are usually managed surgically. However, 30-40% of SFTs will relapse local-regionally or metastasize. There are no systemic therapies with durable activity for malignant SFTs to date. The molecular hallmark of SFTs is a gene fusion between the NAB2 and STAT6 loci on chromosome 12, resulting in a chimeric protein of poorly characterized function called NAB2-STAT6. We use primary samples and an inducible cell model to discover that NAB2-STAT6 operates as a transcriptional coactivator for a specific set of enhancers and promoters that are normally targeted by the EGR1 transcription factor. In physiological conditions, NAB2 is primarily localized to the cytoplasm and only a small nuclear fraction is available to operate as a co-activator of EGR1 targets. NAB2-STAT6 redirects NAB1, NAB2, and additional EGR1 to the nucleus and bolster the expression of neuronal EGR1 targets. The STAT6 moiety of the fusion protein is a major driver of its nuclear localization and further contributes to NAB2’s co-activating abilities. In primary tumors, NAB2- STAT6 activates a neuroendocrine gene signature that sets it apart from most sarcomas. These discoveries provide new insight into the pathogenesis of SFTs and reveal new targets with therapeutic potential.
... In these nine cases, areas with the classic SFT pattern were seen only focally, and staghorn vessels were inconspicuous (O'Regan et al., 2009). In these situations, due to marked collagenization and hypocellularity, sclerotic fibroma, desmoplastic fibroma, and myofibroma should be included in the morphological differential diagnosis (Gengler et al., 2006;O'Regan et al., 2009). Although none of our cases showed a predominance of the fibrous component, it is essential to be aware that these tumors exhibit a broad spectrum of morphological presentations. ...
... Although Bcl-2 positivity can be useful in differentiating SFTs and mesotheliomas, it is less useful for extrapleural SFTs because many soft tissue tumors such as schwannoma, gastrointestinal stromal tumors, and synovial sarcoma can also be BCL-2 positive (Chilosi et al., 1997;O'Regan et al., 2009). On the other hand, positivity for CD99 is quite variable in SFTs (26%-70%; Alawi et al., 2001;Gengler et al., 2006;Renshaw et al., 1995) and is not even reported in some case series (de Morais et al., 2020;Nunes et al., 2020). In the present series, CD99 was performed in only 8 cases and diffusely positive in 5 (62.5%; ...
Objective: To report the clinicopathologic features of 19 oral solitary fibrous tumors (SFTs).
Methods: Clinical data were collected from the records of seven pathology services. All cases were re-evaluated by HE staining and confirmed by immunohistochemistry.
Results: The series comprised 11 females (57.9%) and 8 males (42.1%), with a mean age of 47.3 ± 14.7 years (range: 22-71 years) and a 1.3:1 female-to-male ratio. Most tumors affected the buccal mucosa (n = 7; 36.8%) and presented clinically as an asymptomatic solitary submucosal well-circumscribed nodule with coloration similar to the oral mucosa. Morphologically, most SFTs (n = 10; 52.6%) exhibited a classic hybrid pattern characterized by a well-circumscribed proliferation of densely cellular areas alternating with hypocellular areas in a variably collagenous vascular stroma. Remnants of accessory salivary glands were observed in two cases (n = 2; 10.5%). All tumors were positive for STAT6 and CD34 (n = 19; 100%). Outcome information was available from 6 patients (31.6%), with clinical follow-up ranging from 6 to 24 months (mean ± SD, 9.5 ± 6.8 months), and none developed local recurrence.
Conclusions: Oral SFTs are rare and often clinically misdiagnosed. Pathologists should consider SFT in the differential diagnosis of oral spindle cell tumors. Accurate diagnosis requires careful morphological evaluation supported by immunohistochemical analysis.
Keywords: connective tissue diseases; diagnosis; oral pathology; solitary fibrous tumor.
... Immunohistochemistry is essential for differentiating it from other spindle cell neoplasms. Positivity for CD34, CD99, and bcl-2 is an indicator of SFT (2,5). However, CD34 is absent in 5%-10% of SFT cases, and malignant SFT may be negative for CD34, which is caused by dedifferentiation of the tumor and indicates poor prognosis (5,10). ...
... Positivity for CD34, CD99, and bcl-2 is an indicator of SFT (2,5). However, CD34 is absent in 5%-10% of SFT cases, and malignant SFT may be negative for CD34, which is caused by dedifferentiation of the tumor and indicates poor prognosis (5,10). ...
Solitary fibrous tumors (SFTs) commonly arise from the pleura and are mostly benign. However, they may develop anywhere in the body, and 10%-30% are malignant. Classically, SFTs appear as solitary enhancing masses, and bilateral presentation is extremely rare. In this case, an 88-year-old male presented with back pain and a history of chronic tuberculous empyema. Imaging studies revealed bilateral paravertebral masses with aggressive radiologic features, which were speculatively presumed as thoracic malignancies in association with chronic empyema. Herein, we report a unique case of bilateral paravertebral malignant SFTs that were accurately diagnosed with a CT-guided coaxial needle biopsy.
... The diagnostic criteria for HPC were refined and features for assessment of malignancy were established by Enzinger and Smith in a large study of 106 cases [14]. For many years, HPC and SFTs were considered as two histological subtypes of a single neoplasm due to their clinicopathological similarities [15,16]. The discovery of a shared unifying molecular signature between both tumors, which is the recurrent fusion of NAB2 and STAT6 genes located at chromosomal region 12q13, has confirmed their identical nature [8,9]. ...
Solitary fibrous tumors (SFTs) represent a rare subset of mesenchymal neoplasms, affecting 1–2 per million people, with no gender preference. They demonstrate indolent behavior, frequent asymptomatic presentation, and widespread anatomical involvement. At imaging, SFTs typically appear as well-defined, predominantly hypervascular masses with varying degrees of cystic change and necrosis, though calcification is rare. Avid heterogeneous enhancement is typical following intravenous contrast administration, with multiple blood vessels observed at the periphery. Although findings on CT and MRI alone are generally nonspecific, a frequent feature of SFTs at MRI is the presence of rounded or linear low signal intensity foci on T1- and T2-weighted images, corresponding to the fibrous and collagenous content. Nevertheless, because the imaging features of SFTs overlap with those of many benign and malignant tumors, histologic confirmation is required for the final diagnosis. A comprehensive understanding of SFTs’ multifaceted clinical, pathological, and radiological presentations across various organs is crucial for accurate diagnosis and effective management.
Critical relevance statement
A comprehensive understanding of the classic radiological and pathological features of solitary fibrous tumors across various organs is crucial for accurate diagnosis and effective management.
Key Points
Solitary fibrous tumors (SFTs) are rare hypervascular fibrous tumors with indolent behavior.
Imaging features of SFTs overlap with many other tumors, necessitating histologic confirmation.
Understanding SFTs’ radiological presentations is crucial for accurate diagnosis and effective management.
Graphical Abstract
... The World Health Organization classifies these tumours as neoplasms of pluripotent fibroblastic or myofibroblastic origin [2]. Pathological classification includes a well-defined, lobulated firm mass which is fibrous, with a whorled appearance with intermixed areas of cystic degeneration, calcification, haemorrhage and necrosis macroscopically [3]. Microscopically, they consist of 'whorls of reticulin and collagen with interspersed spindle-shaped cells [2]. ...
Journ a l o f O rt hoped ic O n c ol ogy Shah et al., J Orthop Oncol 2022, 8:6 Abstract Introduction: Solitary fibrous tumours (SFTs) are rare spindle cell neoplasms and have been described according to location as intra-thoracic and extra-thoracic. The World Health Organization classifies SFT as having intermediate malignant potential with low risk of metastasis. Initially extra-thoracic SFTs (ESFT) were considered to be benign with lower rates of mortality when compared to their thoracic counterpart. However, more recent series have found that ESFT behave more aggressively than previously thought. Our tertiary referral centre for soft tissue sarcoma has seen a significant proportion of aggressive disease associated with ESFT.
... Hemangiopericytoma was once used as a synonym for SFT occurring extra-pleura. Subsequently, giant cell angiofibroma and hemangiopericytoma were removed from the WHO classification of soft tissue tumors in 2013, with the former being classified as SFT outside the pleura, which was described as one morphologic variant, while the latter was recommended to be disregarded as a lot of soft tissue tumors could display a hemangiopericytomatous vasculature (3,4). In addition, the NAB2-STAT6 gene fusion was identified in SFTs in 2013 (5). ...
Solitary fibrous tumors (SFTs) are classified as fibroblastic/myofibroblastic tumors that originate from CD34-positive dendritic cells and usually occur in the pleura. In this paper, we describe a case of SFT within the joint cavity of the left knee. A 60-year-old man was admitted to hospital due to swelling in the left knee for the past 8 months without relevant trauma history. X-ray, computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography–computed tomography (PET-CT) presented a large, ill-circumscribed, hypervascular, and highly enhanced mass with eccentric calcification and peripheral, intra-lesional vessels. Subsequently, the patient underwent surgical resection. Postoperative pathology confirmed the neoplastic cells to be positive for CD34, Bcl-2, and SATA6, therefore was finally diagnosed as malignant SFT. The patient developed bone metastases within 1 year after surgery. SFT in the joint cavity is rare, and it is difficult to make a preoperative diagnosis.
... In 2003, Marchevsky et al. [7]. characterized a mediastinal tumor that was predominantly comprised of epithelioid cells, and subsequently coined the term "epithelioid SFTs" to describe this rare entity [5]. ...
Background
Solitary fibroous tumors (SFTs) are distinctive soft tissue tumors characterized by rearrangements of NAB2-STAT6 gene, which are associated with thin-walled, branching, “staghorn”-shaped vessels. SFTs are originally classified as a type of hemangiopericytoma (HPC). Classical SFTs are composed of spindle to ovoid cells arranged haphazardly or in fascicles. Rarely, SFTs exhibit unusual morphological variants such as fat formation, giant cells, dedifferentiation, or epithelioid variant. The epithelioid cell variant, which is composed almost entirely of epithelioid cells and arranged in solid or nest patterns, is extremely rare and frequently malignant.
Case presentation
In this study, we reported three cases of epithelioid SFTs (ESFTs) located in extrathoracic sites (right lateral ventricle, right lumbar, left pelvis). All the subjects in this study were elderly, with a predominance of female patients, accounting for two out of the three cases, and only one case involved a male patient. The tumor cells were entirely composed of epithelioid cells and exhibited positive for CD34 and STAT-6 markers. Ultimately, the majority of cases (two out of three) were diagnosed as malignant SFTs.
Conclusion
This study aims to enhance the awareness of ESFTs. In these cases, irrespective of the onset location, the arrangement patterns of tumor cells, such as papillary structures and the morphology of epithelial-like cells, conspicuously lack the hallmark histological characteristics of Solitary Fibrous Tumors (SFTs). Consequently, it requires differential diagnosis from a plethora of malignant neoplasms. Moreover, the elevated malignancy level of this cohort of cases poses substantial diagnostic challenges to pathologists, compounding the complexity of accurate interpretation.
... Given the potential for local aggressiveness and recurrence, complete surgical excision with negative margins remains the cornerstone of treatment for HPC. Adjuvant radiotherapy is often employed in cases with a high risk of recurrence or when complete resection is not feasible [8]. Due to the rarity of this tumour, especially in the EAC, this case report aims to contribute to the existing literature by documenting the clinical presentation, diagnostic process, and successful management of HPCs in this unusual location. ...
Hemangiopericytomas (HPCs) are rare vascular tumors originating from pericytes, with a predilection for the musculoskeletal system and occasional occurrence in the head and neck region. HPCs arising in the external auditory canal (EAC) are exceptionally rare, making their diagnosis and management a clinical challenge. A 71-year-old male presented with a six-month history of a painless, progressively enlarging mass in his right EAC, accompanied by tinnitus and hearing loss. Physical examination revealed a mobile, reddish mass in the concha of the left auricle, nearly occluding the EAC. Contrast-enhanced computed tomography of the temporal bone demonstrated a heterogeneously enhancing mass with erosion of adjacent structures. Histopathological examination and immunohistochemistry confirmed the diagnosis of an HPC. The tumor was surgically excised, and the patient underwent adjuvant radiotherapy. Over a two-year follow-up period, no recurrence was observed. This case highlights the rarity of HPCs in the EAC and underscores the importance of considering this diagnosis in patients presenting with atypical EAC masses. A multidisciplinary approach, including surgical excision and radiotherapy, is crucial for achieving favorable outcomes and reducing the risk of recurrence. Long-term follow-up is essential due to the potential for late recurrence.
... A finales de la década de los 80, y durante la de los 90, con la llegada de nuevos avances y evidencias en los campos de la inmunohistoquímica y la microscopia electrónica, volvió a tomar fuerza la idea del origen submesotelial de esta neoplasia. Su naturaleza fue definida como eminentemente mesenquimal de manera inequívoca, y la confusa terminología anteriormente empleada fue reemplazándose progresivamente en favor de la actual 9 . Los TFS comenzaron a ser descritos en múltiples localizaciones, demostrándose que dicha lesión no era específica de la pleura u otras cavidades serosas. ...
Los tumores fibrosos solitarios son neoplasias mesenquimales infrecuentes que pueden desarrollarse en cualquier parte del organismo, siendo aquellos que se asientan intracranealmente confundidos con meningiomas por norma general. Presentamos el caso de un varón de 57 años remitido a nuestro centro presentando cuadro de cefalea bifrontal, anosmia y alteración del comportamiento de 6 meses de evolución. Los estudios radiológicos revelaron la existencia de una gran masa tumoral de apariencia extra-axial y localización en fosa craneal anterior, inicialmente compatible con un meningioma gigante del surco olfatorio. Se llevó a cabo la resección quirúrgica radical de la lesión. El diagnóstico anatomopatológico resultó inesperado: un tumor fibroso solitario (grado 1 de la OMS, 2021). Dada la naturaleza agresiva de estas lesiones, con tendencia a la recidiva, transformación maligna e incluso metastatización, la cirugía con intención resectiva macroscópicamente completa debe constituir la primera opción terapeútica. El seguimiento clínico-radiológico estrecho tras el procedimiento está justificado.
... Its nature was unequivocally defined as eminently mesenchymal and the confusing terminology previously used was progressively replaced by the current nomenclature. 9 SFT began to be reported in multiple locations, demonstrating that the lesion was not specific to the pleura or other serous cavities. In fact, 1996 was considered by some authors as the year of the SFT. 10 The history of SFT paralleled that of haemangiopericytoma (HPC), a lesion of uncertain histology rich in capillary structures and perivascular cells described by Stout and Murray in 1942. ...
Solitary fibrous tumors are rare mesenchymal neoplasms that can develop in any part of the body, with those that settle intracranially being confused with meningiomas as a general rule. We present the case of a 57-year-old man referred to our hospital due to bifrontal headache, anosmia, and behavioral alterations of 6 months' duration. Radiological studies revealed the existence of a large tumor mass with an extra-axial appearance and location in the anterior cranial fossa, initially compatible with a giant meningioma of the olfactory groove. Gross total resection of the mass was carried out. The pathological diagnosis was unexpected: a solitary fibrous tumor (WHO grade 1, 2021). Given the aggressive nature of these lesions, with a tendency to recurrence, malignant transformation and even metastasis, surgery with macroscopically complete resection intention should constitute the first therapeutic option. Close clinical-radiological follow-up after the procedure is justified.
... Hemangiopericytoma is a type of tumor thought to come from Zimmerman pericytes displaying signs of myoid or myofibroblast differentiation. [3][4][5] The World Health Organization has classified hemangiopericytoma as a solitary fibrous tumor (SFT) that occurs outside the pleura as either benign or malignant with an overall incidence of 0.6%. While there have been twenty documented instances of hemangiopericytoma, the literature only mentions four cases of hemangiopericytoma. ...
The greater omentum primary malignant tumors are rare, with less than 50 cases reported. Malignant hemangiopericytomas constitute only four of these cases. The common clinical manifestations of a malignant omental tumor are abdominal mass and pain. We report on a woman 38 years old who came to the hospital’s emergency department with a finding consisting of intestinal obstruction (abdominal pain, constipation, abdominal distention, and vomiting), and during a clinical examination a mass was discovered in the lower half of her abdomen. She had been experiencing these symptoms for three days before her arrival. During a clinical examination, a large size, hard mobile mass was discovered in the lower half of her abdomen. The patient underwent an abdominal CT scan which indicated the presence of a sizable, soft tissue mass located within the abdominal and pelvic region, exerting pressure on the small bowel loops, with mild free ascites. Due to the patient's acute abdomen, an exploration laparotomy was performed, revealing a large mass in the omentum measuring 20×20×10 cm and weighing 3 kg. The mass, along with the omentum, was completely removed, and histopathology confirmed a malignant hemangiopericytoma.
... El perfil del tumor es característico: positividad difusa para CD34, el cual es considerado el marcador para los TFS, el 70% de estos tumores expresan CD99 y Bcl-2, y solamente el 20-35% son variablemente positivos para EMA y actina de músculo liso. En general, los TFS expresan negatividad para citoqueratina, actina de músculo liso, S-100 y c-kit 5 . ...
... √Ÿ ª∑' Ë 2 · ¥ß≈-°…≥-¢Õß ‡´≈≈å ‡π◊ È ÕßÕ°√Ÿ ª°√-«¬"π‚´≈' ∑"√' ‰ø∫√-∑Ÿ ‡¡Õ√ǻ÷ Ë ß¡' π' « ‡ §≈' ¬ ‚ª√à ß π' « §≈' ‚Õ≈-‰¡à ‡¥à π™-¥ ·≈-‰´‚∑ae≈"´÷ ¡πâ Õ¬ (¬â Õ¡ ' OE' ¡"∑Õ°´' ≈' π·≈-Õ' ‚Õ´' π °"≈-ߢ¬"¬ 400 ‡∑à ") ≈-°…≥-·µ°·¢πß §≈â "¬ ‡¢"°«"ß (√Ÿ ª∑' Ë 1) 33,34 ‡´≈≈å ‡π◊ È Õ ßÕ°¡' √Ÿ ª√à "ß §≈â "¬°√-«¬ π' « ‡ §≈' ¬ ‚ª√à ß (vesicular nuclei) π' « §≈' ‚Õ≈-‰¡à ‡¥à π™-¥ ‰´‚∑ae≈"´÷ ¡πâ Õ¬ ·≈-‰¡à §à Õ¬ae∫ ‡´≈≈å ∑' Ë°"≈-ß·∫à ßµ-« (√Ÿ ª∑' Ë 2) πÕ°®"°π' È Õ"®ae∫¡-¥"¬ §Õ≈≈" ‡®π §≈â "¬·º≈ ‡ªì π (keloid-like bundle of collagen) °"√ -¡¢Õß°â Õπ· §≈ ‡´' ¬¡·≈- ‡π◊ È Õµ"¬‰¥â 10,19 ∫"ß §√-È ß¿"¬"π ‡π◊ È ÕßÕ°Õ"®ae∫ ‡´≈≈å ‰¢¡-π (adipocyte) 34 ·≈- ‡´≈≈å ¢π"¥"À≠à À≈"¬π' « ‡ §≈' ¬ (giant multinucleated cells) ‰¥â 35 "À√-∫‚´≈' ∑"√' ‰ø∫√-∑Ÿ ‡¡Õ√å "π™à Õߪ"°¡' √"¬ß"π «à "Õ"®ae∫¡" µå ‡´≈≈å (mast cell) ®"π«π¡"°"π™' È π ‡π◊ È Õ 36 ÷ Ë ß "¡"√∂µ√«® Õ∫ ‡ae' Ë ¡ ‡µ' ¡‚¥¬°"√¬â Õ¡ ' ‚∑≈Ÿ Õ' ¥' π∫≈Ÿ (toluidine blue) 37°" √µ√«®∑"ßÕ' ¡¡Ÿ ‚πOE' ‚∑ ‡ §¡'°" √«' π' ®©-¬‚´≈' ∑"√' ‰ø∫√-∑Ÿ ‡¡Õ√å µâ ÕßÕ"»-¬°"√¬◊ π¬-π ¥â «¬«' ∏' Õ' ¡¡Ÿ ‚πOE' ‚∑ ‡ §¡' ‚¥¬ae∫«à " ‡´≈≈å ‡π◊ È ÕßÕ°¡'°"√ · ¥ßÕÕ°¢Õß‚ª√µ' π ´' ¥' 34 (CD34) (√â Õ¬≈-90-95) (√Ÿ ª∑' Ë 3) ´' ¥' 99 (CD99) (√â Õ¬≈-50-75) ·≈-∫'' ·Õ≈-2 (bcl-2) (√â Õ¬≈-20-35) 10,38 ·≈-‰¡à ¡'°"√· ¥ßÕÕ°¢Õß ‚ª√µ' π·Õ°∑' π¢Õß°≈â "¡ ‡π◊ È Õ ‡√' ¬∫ ‰´‚∑ ‡ §Õ√"∑' π (cytokeratin) ‡Õ -100 (S-100) ‡¥ ¡' π (desmin) ·ø° ‡µÕ√å 13 ‡Õ (factor XIIIa) ·≈- ‡Õae' ∑' ‡≈' ¬≈ ‡¡¡ ‡∫√π·Õπµ' ‡®π (epithelial membrane antigen) 39,40 πÕ°®"°π' È ‡´≈≈å ‡π◊ È ÕßÕ°"π‚´≈' ∑"√' ‰ø∫√-∑Ÿ ‡¡Õ√å ¡'°"√ · ¥ßÕÕ°¢Õß ‡ §‰Õ-67 (Ki-67) §à Õπ¢â "ßµË " 36 ‚¥¬¡' √"¬ß"πae∫°"√· ¥ßÕÕ°¢Õß‚ª√µ' π™π' ¥π' È ∑' Ë π' « ‡ §≈' ¬ √â Õ¬≈-1-10 ¢Õß ‡´≈≈å ∑-È ßÀ¡¥ [41][42][43] ·µà°"√· ¥ßÕÕ°¢Õß ‡ §‰Õ-67 Õ"® ‡ae' Ë ¡¢÷ È π∂÷ ß√â Õ¬≈-20 "π√Õ¬‚√ §∑' Ë · ¥ß≈-°…≥- ‡π◊ È ÕßÕ°√ â "¬·√ß 42°" √«' π' ®©-¬·¬°‚√ §°" √«' π' ®©-¬·¬°‚√ §∑"ß®ÿ ≈ae¬"∏' «' ∑¬"¢Õß‚´≈' ∑"√' ‰ø∫√-∑Ÿ ‡¡Õ√å πÕ°®"°®-µâ Õß·¬°ÕÕ°®"°OE' ·¡ß®' ‚Õ ‡aeÕ√' ‰´‚∑¡"·≈â « §«√·¬°ÕÕ°®"° ‡π◊ È ÕßÕ°¢Õß ‡π◊ È Õ ‡¬◊ Ë ÕÕà ÕπÀ≈"¬ ™π' ¥∑' Ë ¡' ‡´≈≈å √Ÿ ª°√-«¬ ‡ªì πÕß §å ª√-°Õ∫ ‡™à π ‰¡‚Õ‰ø‚∫√¡" ‰ø‚∫√¡"‚∑´' (fibromatosis) ‰ø∫√-OE' ∑' ‚Õ‰´‚∑¡"·≈- ‡π◊ È ÕßÕ°¢Õߪ≈"¬ª√-"∑ (peripheral nerve sheath tumor) ...
... SFTs share a similar growth pattern with haemangiopericytomas (HPCs) and can be classified as HPC-like neoplasms. Three groups of HPC-like neoplasms can be identified: non-HPC neoplasms, which occasionally display HPC-like features (e.g., synovial sarcoma); lesions with clear evidence of myoid/pericytic differentiation (true HPCs); and fibrous-tocellular SFTs and related lesions such as giant cell angiofibromas and lipomatous HPCs (4). ...
Introduction: Solitary fibrous tumor (SFT) is a rare mesenchymal tumor that usually arises from the pleura but can also occur in extrapleural sites, such as the sinonasal region. It causes aspecific symptoms, including nasal obstruction and discharge, postnasal drip, anosmia, epistaxis, and headache. It may be difficult to distinguish these symptoms from those caused by other mesenchymal lesions that usually occur in this site, especially when the tissues undergo iatrogenic damage following surgical removal.
Case Report: This case report shows a rare right nasal septal solitary fibrous tumor, which was surgically removed using a trans-nasal endoscopic technique. For the first time, the mass was decomposed by a plasma blade, and the implant site was treated by performing a subperiosteal removal of septal mucosa and cartilage. Histopathological examination confirmed the diagnosis of solitary fibrous tumor. Follow-up at three, six, and twelve months showed no signs of relapse.
Conclusions: Sinonasal SFT is unusual, and it may be difficult to distinguish it from other mesenchymal lesions in this site. In the literature, cases treated with CO2 laser are usually described; however, due to the high cutting temperatures, this can cause thermal damage of the tissues, making histopathological diagnosis difficult. The plasma blade uses pulsed radiofrequency, creating an effective cutting edge while the blade stays near body temperature. Therefore, this device results in atraumatic, scalpel-like cutting sensitivity and electrosurgical-like hemostasis, with minimal bleeding and tissue injury. Its use could, therefore, help both the surgeon in obtaining surgical radicality and the pathologist in the correct histologic classification.
... This pattern is a storiform arrangement of spindle cells combined with a "hemangiopericytoma-like appearance" and increased vascularity of the lesion. 11 Other differential diagnoses include spindle cell F I G U R E 2 Laparoscopic image of the mass (arrow) seen during dissection. ...
Key Clinical Message
Primary retroperitoneal masses have numerous differential diagnoses, many of which are rare entities. These can be neoplastic or nonneoplastic. Among the rare conditions are solitary fibrous tumors, which can either be benign or malignant. It is a mesenchymal, spindle‐cell tumor, reported first in 1931 as a pleural tumor by Klemperer et al. A 20‐year‐old lady, with abdominal pain for 6 months, was diagnosed with a retroperitoneal mass on the left lower abdomen on USG which was confirmed by an MRI scan of the abdomen. The patient underwent laparoscopy‐assisted excision of the mass. The final histopathological reports and immunohistochemistry reports revealed a solitary fibrous tumor. Solitary fibrous tumors (SFTs) are rare tumors in the retroperitoneum. In our search, fewer than a hundred cases have been reported. It has a characteristic “patternless pattern” in a microscopic study. Adverse outcomes of SFTs are associated with atypical features in histology, such as nuclear pleomorphism, necrosis, increased cellularity, and mitoses >4/10 HPF and size more than 10 cm. The standard of care is surgical excision with clear margins. Open surgeries have been done traditionally; we present a case where we performed the excision laparoscopically.
... Intracranial SFT and HPC were initially reported by Carneiro et al (1) and Begg and Garret (2) in 1996 and 1954, respectively. Due to similar histological features, immunophenotype, and the common chromosome 12q13 inversion, nerve growth factor-induced gene A binding protein 2 (NAB2) and STAT6 gene fusion (3), the World Health Organization (WHO) central nervous system (CNS) classification from 2016 used the joint diagnostic terminology 'Solitary fibrous tumor/hemangiopericytoma' to describe these disorders and classified them into grades I, II and III (4). However, the distinction between the two types was no longer clinically significant due to the pronounced clinical and histopathological overlap (5). ...
Solitary fibrous tumor (SFT) of the central nervous system is a rare fibroblastic tumor of mesenchymal origin. SFTs in the saddle area are much less common. In January 2022, a 43-year-old female patient was admitted with SFT 3 months following partial resection of a microscopic transsphenoidal saddle area tumor at a different hospital. Magnetic resonance imaging indicated that the unresected part of the tumor was significantly enhanced on T1 enhancement, which strongly indicated a recurrence. Subsequently, the patient underwent transnasal endoscopic saddle area tumor resection at our hospital and the tumor was successfully removed. By using postoperative pathology examination, immunohistochemical analysis of Bcl-2, cluster of differentiation 99, STAT6 and vimentin, and a fusion gene test performed by high-throughput sequencing technology, the SFT was definitively diagnosed. Following 3 months of follow-up, the patient was found to have tumor recurrence in the cavernous sinus and absence of tumor growth in the pituitary fossa. Therefore, the patient received proton therapy and tumor growth was controlled effectively.
... In the case of solitary fibrous tumors, the incidence in the pleural cavity is >50%. The incidence of extrapleural disease is only 0.6% and rarely affects the head and neck (13). In terms of MRI scan, T1-weighted imaging (T1WI) showed an equivalent signal, T2WI an uneven hypersignal and enhancement a moderate to obvious enhancement. ...
Aggressive fibromatosis (AF), also known as ligamentoid fibromatosis and desmoid tumor, is a fibroblast clonoproliferative lesion located in the deep soft tissue. The present study reports the case of a 36-year-old female with AF who underwent cervical spinal cord ependymoma surgery. AF developed in the soft tissue of the neck adjacent to the incision site. The size of the neck AF increased rapidly over 2 years, and due to discomfort, the patient underwent initial surgical resection without any other combined treatment methods. When the patient was routinely reviewed at 6 months post-surgery, a recurrence of AF of the neck was found. The patient was recommended surgical resection and radiotherapy. This case report should improve the understanding of clinicians with regard to AF, and help the diagnostic process and treatment plan.
... This entity was initially considered as a variant of hemangiopericytomas (HPC) 6 . Nowadays, the term SFT expanded to include both, pleural SFT and most tumors previously branded as HPC 7 . About 10%-15% of SFT show malignant behavior 3 . ...
Solitary fibrous tumor (SFT) is a spindle cell neoplasm of mesenchymal origin. First reported in 1931, the pleura is the most common localization of SFT, and it’s exceptionally rare in the kidney. Overall, it represents less than 2% of all soft tissue tumors. In most cases, renal SFT (rSFT) presents with hematuria, flank pain, and a palpable mass. To our knowledge, less than 112 cases of rSFT have been reported. We report a case of rSFT of a 30-year-old male thought to be a renal cell carcinoma (RCC). Radical nephrectomy (RN) was done to remove a large right-sided mass invading the inferior vena cava. Immunohistochemistry confirmed the diagnosis of SFT showing positivity for CD34, CD99, and Bcl-2 protein, with no staining for cytokeratin. A post-operative CT (15 months) showed tumor recurrence in the renal compartment with huge inferior vena cava thrombus extending to the external iliac veins. With this case, we illustrate and highlight the importance of this diagnosis because of the uncertain biological behavior and prognosis of these tumors.
... Solitary fibrous tumors (SFT), including hemangiopericytoma (HPC) or HPC-like lesions, are rare spindle-cell neoplasms that can occur in any region of the body (Gengler, Guillou, 2006). ...
The aim of this study was to better characterize head and neck solitary fibrous tumors (SFTs) and to evaluate surgical treatment. This retrospective study included patients who presented with head and neck SFTs. Clinical, radiological, and histological information and data regarding the treatments performed were collected. The risk of locoregional and distant metastases was calculated, and for orbital SFTs a specific classification was used. Overall, 34 patients were included. The majority of the SFTs were found in the oral cavity (n = 10), followed by the neck region (n = 8). The mean time to recurrence was 67.4 months. All patients underwent primary surgical resection. Recurrence was observed in five patients with a low risk of locoregional recurrence and distant metastasis. The treatment of choice is complete resection. Recurrence seems to be highly correlated with positive surgical margins. The safety margin should be increased when removing the lesion, and long-term follow-up should be performed.
... [7] Extra-thoracic SFT shares similar histological, immunohistochemical and ultrastructural features to those arising from pleura based intrathoracic tumors. [8] Relative proportion of cells and fibrous stroma determine the appearance of SFT. The cellular areas consist of tightly packed round to fusiform cells arranged around a continuous ramifying vascular network (staghorn or antler like). ...
Solitary fibrous tumor (SFT) is a fibroblastic mesenchymal neoplasm that rarely metastasizes. SFTs was first described in relation to pleura. However, occurrence of this tumor type has been reported in other sites like peritoneum, liver, adrenal gland, meninges and oral cavity. In head and neck region, oral cavity is the most common site of involvement. Most of the solitary fibrous tumors are benign and present as an asymptomatic slow growing mass. Surgery remains the mainstay of treatment. Hereby, we describe a case of 71-year-old male with malignant solitary fibrous tumor arising from right maxilla invading the right orbit presenting as proptosis.
... Microscopic features alone are insufficient to confirm the diagnosis of SFT and further IHC analysis must be conducted. SFT cells typically stain positive for specific markers, such as CD34 and STAT6, and variably positive for vimentin, S-100 protein, progesterone receptors (PR), P53, BCL-2, and Ki-67 [19]. CD34, an antigen expressed on endothelial cells and hematopoietic progenitor cells, stained strongly and diffusely, and it is believed to be the most diagnostic immunohistochemical biomarker for benign SFTs. ...
Background
Spindle cell tumors, called solitary fibrous tumors (SFTs), are of mesenchymal origin, and can develop in the orbit. As ‘intermediate malignancy’ tumors, only a small percentage show malignant behavior, such as invasion of surrounding tissue.
Case presentation
A 57-year-old woman presented with a 19-year history of a giant right orbital mass. Orbital computed tomography (CT) revealed an inhomogeneously-enhancing mass compressing and engulfing the eyeball and optic nerve. She underwent lid-sparing orbital exenteration. Microscopic characteristics and immunohistochemistry (IHC) tests were indicative of a benign SFT. No recurrence was observed at the 4-year follow-up.
Conclusion
Early and complete tumor resection is recommended.
... In practice, any HPC-like lesion can be allocated to one of these categories, leaving the ill-defined "haemangiopericytoma" category empty. 12 Glomangiopericytoma is defined as a sinonasal tumor with perivascular myoid phenotype, which accounts for less than 0.5% of all sinonasal tumors. Glomangiopericytoma was first reported as hemangiopericytoma in 1942, but this definition has been questioned. 1 The World Health Organization (WHO) classified this tumor as glomangiopericytoma in 2005. ...
... Some suggested histologic features, including mitosis, atypia, and tumor necrosis, 2 of 10 as well as demographic features, including age, tumor size, and location of the tumor as predictors of SFT aggressive behavior. Particularly size and mitotic counts have been emphasized more than others [5,[8][9][10][11][12]. Based on the lack of a histologic grading system, Demicco et al. developed a risk stratification model based on the patient's age, tumor size, mitotic count, and tumor necrosis. ...
Simple Summary
A solitary fibrous tumor (SFT) is a fibroblastic mesenchymal tumor with the hallmark of an NAB2–STAT6 gene fusion and an intermediate tendency to metastasize. Based on the lack of a histologic-based grading system for extra-meningeal SFTs, we defined the prognostic value of histologic features that predict the risk of developing distant metastases. Moreover, our study revealed the histologic alterations to recurrent SFTs that affect the biological behavior of the tumor.
Abstract
Histology has not been accepted as a valid predictor of the biological behavior of extra-meningeal solitary fibrous tumors (SFTs). Based on the lack of a histologic grading system, a risk stratification model is accepted by the WHO to predict the risk of metastasis; however, the model shows some limitations to predict the aggressive behavior of a low-risk/benign-appearing tumor. We conducted a retrospective study based on medical records of 51 primary extra-meningeal SFT patients treated surgically with a median follow-up of 60 months. Tumor size (p = 0.001), mitotic activity (p = 0.003), and cellular variants (p = 0.001) were statistically associated with the development of distant metastases. In cox regression analysis for metastasis outcome, a one-centimeter increment in tumor size enhanced the expected metastasis hazard by 21% during the follow-up time (HR = 1.21, CI 95% (1.08–1.35)), and each increase in the number of mitotic figures escalated the expected hazard of metastasis by 20% (HR = 1.2, CI 95% (1.06–1.34)). Recurrent SFTs presented with higher mitotic activity and increased the likelihood of distant metastasis (p = 0.003, HR = 12.68, CI 95% (2.31–69.5)). All SFTs with focal dedifferentiation developed metastases during follow-up. Our findings also revealed that assembling risk models based on a diagnostic biopsy underestimated the probability of developing metastasis in extra-meningeal SFTs.
Solitary fibrous tumor (SFT) is a rare mesenchymal tissue neoplasm that can occur at all anatomic sites, commonly at the pleura. This uncommon mesenchymal tumor can arise in various soft tissues and organs throughout the body, primarily affecting adults and rarely seen in children. In the head & neck region, frequent sites involved are oral cavity, sinonasal tract and orbit. Histopathologically, these tumors are characterized by uniform, spindle-shaped to ovoid fibroblastic cells and a distinctive staghorn vascular pattern. Immunohistochemical analysis reveals that the tumor cells are consistently positive for CD34 and STAT6 in nearly all cases. In this article, we present a rare case of a solitary fibrous tumor located in the mandibular lingual gingiva of a 35-year-old female, with supporting immunohistochemical evidence.
A 55-year-old female presents with a left iliac fossa mass of a few months in duration. An MRI shows a pelvic mass (Fig. 1a). No other evidence of distant metastasis was found in a staging CT chest/abdomen/pelvis. Ultrasound guided biopsy of the mass returned as a spindle and round cell tumour that was positive for CD34, CD99 and had strong nuclear positivity for STAT6. EWSR-1 break-apart FISH was negative. Diagnosis was favouring that of solitary fibrous tumour. The mass of deemed unresectable and she underwent palliative chemotherapy with doxorubicin and dacarbazine. However, best response was that of stable disease.
Solitary fibrous tumors (SFTs) are rare mesenchymal tumors, most commonly occurring in the pleura. Extrapleural cases, particularly in the anterior abdominal wall, are extremely rare. We present a rare case of a malignant SFT arising from the left anterior abdominal wall in an adult patient in their 60s, who presented with a mass in left iliac fossa. The diagnosis was confirmed by tissue biopsy and immunohistochemical analysis. The presented case highlights the rarity of malignant SFTs in the anterior abdominal wall, emphasizing the importance of thorough diagnostic evaluation and surgical management for optimal outcomes.
Glomangiopericytoma is an uncommon tumor of the sinonasal region, originating from the pericytes that envelop capillaries, and it accounts for fewer than half a percent (0.5%) of all sinonasal tumors. This report presents the case of a 65-year-old man who experienced worsening nasal obstruction and was subsequently diagnosed with glomangiopericytoma based on histological, immunohistochemical, and radiographic findings. The patient underwent a complete excision of the tumor via an endoscopic endonasal approach. Upon follow-up after the surgical resection, the patient exhibited no signs of recurrence.
Solitary fibrous tumors (SFTs) are rare mesenchymal tumors characterized by recurrent NAB2::STAT6 gene fusion, which are associated with an unpredictable clinical course, including the potential for recurrence or metastasis. Current therapeutic approaches for relapsed cases remain ineffective, and there is no established standard of care for SFTs. Although patient-derived cancer cell lines are fundamental research tools, only a few cell lines have been developed for SFTs. To address this, we established a novel SFT cell line, NCC-SFT1-C1, derived from surgically resected tumor tissues of a patient with SFT. The cell line retains the characteristic recurrent NAB2::STAT6 gene fusion in concordance with the matched original tumor. These cells exhibit moderate proliferation, invasion ability, and spheroid formation. We demonstrated that NCC-SFT1-C1 cells are useful for the high-throughput screening of the antiproliferative effects of 221 oncology drugs. Therefore, the NCC-SFT1-C1 cell line is a valuable tool for basic and preclinical studies on SFT.
Solitary fibrous tumor (SFT) is an uncommon spindle cell neoplasm, which generally arises from the pleura. There have been documented a number of extrapleural origins including the head and neck in the literature. It is emphasized to make a diagnosis in a rare location such as the retropharyngeal space. We present a case of a 54-year-old man diagnosed with giant solitary retropharyngeal SFT. Clinical symptoms were pharyngeal foreign body sensation and dysphagia associated with dyspnea. Physical examination showed a sizable submucosal mass under the posterior pharyngeal wall, which partially obstructed the upper aerodigestive tract. With radiologic images to evaluate the dimension and relationship with surrounding structures, the tumor was surgically removed en bloc via a transcervical approach. The histology and immunohistochemistry play a crucial role in differential diagnosis. Complete surgical excision is an alternative and curative strategy.
The pathogenesis of many rare tumor types is poorly understood, preventing the design of effective treatments. Solitary fibrous tumors (SFTs) are neoplasms of mesenchymal origin that affect 1/1,000,000 individuals every year and are clinically assimilated to soft tissue sarcomas. SFTs can arise throughout the body and are usually managed surgically. However, 30-40% of SFTs will relapse local-regionally or metastasize. There are no systemic therapies with durable activity for malignant SFTs to date. The molecular hallmark of SFTs is a gene fusion between the NAB2 and STAT6 loci on chromosome 12, resulting in a chimeric protein of poorly characterized function called NAB2-STAT6. We use primary samples and an inducible cell model to discover that NAB2-STAT6 operates as a transcriptional coactivator for a specific set of enhancers and promoters that are normally targeted by the EGR1 transcription factor. In physiological conditions, NAB2 is primarily localized to the cytoplasm and only a small nuclear fraction is available to operate as a co-activator of EGR1 targets. NAB2-STAT6 redirects NAB1, NAB2, and additional EGR1 to the nucleus and bolster the expression of neuronal EGR1 targets. The STAT6 moiety of the fusion protein is a major driver of its nuclear localization and further contributes to NAB2's co-activating abilities. In primary tumors, NAB2-STAT6 activates a neuroendocrine gene signature that sets it apart from most sarcomas. These discoveries provide new insight into the pathogenesis of SFTs and reveal new targets with therapeutic potential. Reviewed Preprint v1 • September 4, 2024 Not revised Connor M Hill et al., 2024 eLife. https://doi.org/10.7554/eLife.98072.1 2 of 37 eLife assessment This study provides compelling data regarding the molecular characterization of a rare tumor type with few treatment options. This fundamental work significantly advances our mechanistic understanding of solitary fibrous tumours, a critical first step towards targeted precision medicine approaches. The results of this study will be of broad interest to cancer biologists and experimental oncologists.
Solitary fibrous tumors (SFTs) are fibroblast tumors that occur mainly in the pleura. Hepatic SFT with skeleton metastases was rarely documented. In this case, we report the contrast-enhanced CT, 18F-FDG, and 68Ga-FAPI-46 PET/CT findings of a rare hepatic SFT with bone metastases. 68Ga-FAPI-46 PET/CT showed much higher tumor-to-background contrast of hepatic tumors and revealed more metastatic bone lesions than 18F-FDG PET/CT. This case demonstrated the superiority of 68Ga-FAPI-46 PET/CT over 18F-FDG for identifying metastatic lesions in malignant SFTs. This observation may add information on the benefit of FAPI PET/CT in SFT staging.
Simple Summary
Extrameningeal solitary fibrous tumors (SFTs) are distinct mesenchymal neoplasms with the propensity for recurrence and the characteristic genetic marker of the NAB2-STAT6 fusion gene. These tumors typically present as slow-growing masses, most commonly in the extremities or trunk. Different clinical behaviors ranging from low to high aggressiveness with the potential for metastasis can be observed. Diagnosis is based mainly on immunohistochemical staging for classic CD34 and STAT6 markers, although it can be perplexed by the similarity to other lesions. Surgical resection remains the primary treatment, and long-term follow-up is obligatory due to the unpredictable nature of SFTs. Further research is emerging to understand the biological behavior and optimal management with efficient treatment of SFTs.
Abstract
Solitary fibrous tumors (SFT) are rare mesenchymal neoplasms that account for less than 2% of all soft tissue masses. In the latest WHO 2020 Classification of Soft Tissue Tumors, extrameningeal SFT was listed as intermediate (rarely metastasizing) or malignant neoplasms. Due to the lack of characteristic clinical features, their diagnosis and treatment remain challenging. The pathogenesis of SFT is often associated with the presence of fusions of the NAB2-STAT6 gene on the 12q13 chromosome. Cytoplasmic CD34 positive staining is considerably characteristic for most SFTs; less frequently, factor XII, vimentin, bcl-2, and CD99 are present. A key factor in the diagnosis is the prevalent nuclear location of STAT6 expression. Radical resection is the mainstay of localized SFTs. In the case of unresectable disease, only radiotherapy or radio-chemotherapy may significantly ensure long-term local control of primary and metastatic lesions. To date, no practical guidelines have been published for the treatment of advanced or metastatic disease. Classical anthracycline-based chemotherapy is applicable. The latest studies suggest that antiangiogenic therapies should be considered after first-line treatment. Other drugs, such as imatinib, figitumumab, axitinib, and eribulin, are also being tested. Definitive radiotherapy appears to be a promising therapeutic modality. Since standards for the treatment of advanced and metastatic diseases are not available, further investigation of novel agents is necessary.
Solitary fibrous tumor (SFT), which was initially believed to be a subtype of mesothelioma, has been reported to occur outside the pleura. In the head and neck region, it primarily manifests in the oral or nasal cavity, with rare occurrences in the facial region. A 40-year-old woman visited our hospital with a mass on her chin. Prior to surgery, involuntary movement was observed in the ipsilateral corner of the mouth upon palpation of the mass. Special care was taken during the surgical procedure to avoid damaging the facial nerve. The mass was excised, and histological examination and immunohistochemical analysis confirmed the diagnosis of an SFT. Here, we present the first reported case of an SFT diagnosed in a jaw mass in Korea. The objective of this study was to highlight the importance of the diagnostic accuracy of SFTs in lower jaw masses.
Solitary fibrous tumors (SFTs) are rare mesenchymal tumors with unpredictable evolution and with a recurrence or metastasis rate of 10-40%. Current medical treatments for relapsed SFTs remain ineffective. Here, we identify potential therapeutic targets and risk factors, including IDH1 p.R132S, high PD-L1 expression, and predominant macrophage infiltration, suggesting the potential benefits of combinational immune therapy and targeted therapy for SFTs. An integrated risk model incorporating mitotic count, density of Ki-67+ cells and CD163+ cells, MTOR mutation is developed, applying a discovery cohort of 101 primary non-CNS patients with negative tumor margins (NTM) and validated in three independent cohorts of 210 SFTs with the same criteria, and in 36 primary CNS SFTs with NTM. Compared with the existing models, our model shows significantly improved efficacy in identifying high-risk primary non-CNS and CNS SFTs with NTM for tumor progression.Our findings hold promise for advancing therapeutic strategies and refining risk prediction in SFTs.
Introduction:
Solitary fibrous tumors (SFTs) are uncommon mesenchymal neoplasms that comprise <2 % of all soft tissue tumors. They are a diagnostically challenging group of neoplasms that can occur essentially anywhere. Molecular or genetic testing of soft tissue tumors will increasingly add to the foundation of distinctive histologic features, as accurate diagnosis is critical for appropriate treatment.
Case presentation:
A 28-year-old woman was referred to our hospital for a left breast mass. Ultrasonography showed an oval hypoechoic mass with partially obscured boundaries. Surgical specimens revealed spindle tumor cells surrounding the mammary ducts and were immunoreactive for both CD34 and STAT6, suggesting SFTs. However, the infiltration of spindle tumor cells into the surrounding fat, and the storiform-like pattern made us consider dermatofibrosarcoma protuberans (DFSP) as a differential diagnosis. Lack of amplification of the COL1A1-PDGFB fusion gene, a characteristic feature of DFSP, led to our definitive diagnosis of breast SFT.
Discussion:
The presence of STAT6 in tumor cell nuclei is a highly sensitive immunohistochemical marker for SFT. In our case, morphological features evoked the differential diagnosis of DFSP and we investigated the COL1A1-PDGFB fusion gene. The diagnostic process of reliably performing careful morphological examination and immunohistochemical marker test, and then obtain conviction by molecular cytogenetic technique is more and more important for soft tissue tumors.
Conclusions:
We report a quite uncommon case of breast SFT and excluded DFSP as a differential diagnosis. If it is difficult to distinguish between these diseases, molecular cytogenetic analysis would be required for accurate diagnosis.
Background:
Head and neck solitary fibrous tumors (SFTs) are rare neoplasms, with few large-scale studies describing this entity. We evaluated the demographics and correlates of survival in a large series of SFT patients.
Methods:
The 2004-2017 National Cancer Database was queried for head and neck SFT patients receiving definitive surgery. Cox proportional-hazards and Kaplan-Meier analyses assessed overall survival (OS).
Results:
Of 135 patients, sinonasal (33.1%) and orbital (25.9%) SFTs were most common. Approximately 93% of SFTs were invasive and 64% were classified as hemangiopericytomas. The 5-year OS of skull base SFTs (84.5%) was lower than sinonasal (98.7%) and orbital (90.7%) SFTs (all p < 0.05). Government insurance exhibited higher mortality (HR 5.116; p < 0.001) and lower OS (p = 0.001).
Conclusion:
Head and neck SFTs presented with distinct prognoses based on anatomical origin. Overall survival was particularly worse in patients with skull base SFTs or government insurance. Prognostically, hemangiopericytomas were indistinct from other SFTs.
Objective:
To review the research progress of intraspinal solitary fibrous tumor (SFT).
Methods:
The domestic and foreign researches on intraspinal SFT were extensively reviewed and analyzed from four aspects, including disease origin, pathological and radiological characteristics, diagnosis and differential diagnosis, and treatment and prognosis.
Results:
SFT is an interstitial fibroblastic tumor with a low probability of occurrence in the central nervous system, especially in the spinal canal. In 2016, the World Health Organization (WHO) used the joint diagnostic term "SFT/hemangiopericytoma" according to the pathological characteristics of mesenchymal fibroblasts, which can be divided into three levels according to specific characteristics. The diagnosis process of intraspinal SFT is complex and tedious. It has relatively variable imaging manifestations and specific pathological changes of NAB2-STAT6 fusion gene, which often requires differential diagnosis with neurinoma, meningioma, etc. The treatment of SFT is mainly resection, which can be assisted by radiotherapy to improve the prognosis.
Conclusion:
Intraspinal SFT is a rare disease. Surgery is still the main treatment. It is recommended to combine preoperative or postoperative radiotherapy. The efficacy of chemotherapy is still unclear. In the future, more studies are expected to establish a systematic diagnosis and treatment strategy for intraspinal SFT.
Intermediate filament proteins and actin isoforms of a series of 12 malignant hemangiopericytomas and five glomus tumors were examined by light microscopy, transmission electron microscopy, two-dimensional gel electrophoresis (2D-GE), and by immunohistochemistry, the latter using monoclonal or affinity-purified polyclonal antibodies to desmin, vimentin, cytokeratins, alpha-smooth muscle, and alpha-sarcomeric actins. By light microscopy, all hemangiopericytomas disclosed a predominant vascular pattern with scant storiform, myxoid and spindle cell areas, and with variable degrees of perivascular fibrosis. By ultrastructure, smooth muscle differentiation was observed in each hemangiopericytoma. Immunohistochemically, neoplastic cells of hemangiopericytomas expressed vimentin as the sole intermediate filament protein and lacked alpha-smooth muscle or alpha-sarcomeric actins. 2D-GE revealed only beta and gamma actins, in proportions typical for fibroblastic tissues. Glomus tumors revealed vimentin and alpha-smooth muscle actin within glomus cells by immunohistochemical techniques and disclosed ultrastructurally distinct smooth muscle differentiation. Therefore hemangiopericytomas represent a distinct soft-tissue neoplasm with uniform morphologic, immunohistochemical, and biochemical features most likely related to glomus tumors, the former representing an aggressive and potentially malignant neoplasm of vascular smooth muscle cells and the latter a well-differentiated neoplasm of vascular smooth muscle cells. Because malignant hemangiopericytomas disclose smooth muscle differentiation by ultrastructure, but do not express alpha-smooth muscle actin, as normal pericytes and glomus cells, it is suggested that these neoplasms represent highly vascularized smooth muscle neoplasms, ie, poorly differentiated leiomyosarcomas derived from vascular smooth muscle cells or their equivalent, the pericytes, which have lost alpha-smooth muscle actin as a differentiation marker that is similar to many conventional poorly differentiated leiomyosarcomas.
Localized fibrous tumor of the serosal cavities (localized fibrous mesothelioma) is a generally benign spindle cell neoplasm of uncertain histogenesis. Fourteen histologically similar primary tumors from different mesothelium-lined sites (11 pleural and 1 each in the pericardium, peritoneal cavity, and pouch of Douglas) and 2 recurrences of those tumors (pericardium and pouch of Douglas) were examined histopathologically and by flow cytometry to relate histologic features and DNA ploidy to biologic behavior (follow-up, 48-255 months among 13 patients). All 16 tumors (14 primaries and 2 recurrences) displayed diploid DNA pattern, and none of 13 patients died of disease (1 patient was lost to follow-up). To elucidate the histogenesis, seven primary tumors were examined for vimentin and keratin immunostaining and six primary tumors were assessed by electron microscopy. All cases exhibited spindle-fibroblastic cell proliferation with a prominent hemangiopericytic pattern. All cases so examined had positive results for vimentin and negative results for keratin. Ultrastructurally, the tumor cells showed mesenchymal-fibroblastic features. These results support a mesenchymal origin, most likely from submesothelial fibroblasts. Further, this neoplasm may recur but retain its basic histologic features, diploidy, and benign outcome.
alpha-Smooth muscle (alpha-sm) actin, an isoform typical of smooth muscle cells (SMC) and present in high amounts in vascular SMC, was demonstrated in the cytoplasm of pericytes of various rat and human organs by means of immunocytochemistry at the electron microscopic level. In SMC and pericytes, alpha-sm actin was localized in microfilament bundles, strengthening the assumption that it is the functional isoform in these cell types and supporting the assumption that pericytes exert contractile functions.
Context.—Solitary fibrous tumors (SFTs) of the central nervous system are rare neoplasms that usually present as dura-based masses and clinically resemble meningiomas. Histologically, they can be similar to fibrous meningioma or hemangiopericytoma (HPC). In particular, densely cellular regions seen in some SFTs can be indistinguishable from HPC. Little is known about the biological behavior of SFTs, although most seem amenable to total resection.
Objectives.—To define the clinicopathologic spectrum of SFTs in the central nervous system and to outline their differences from HPC and meningioma.
Design.—We present the clinicopathologic features of 18 patients with SFT and compare them with those of an age- and sex-matched cohort of HPCs.
Results.—Eleven SFTs were supratentorial, 3 were infratentorial, and 4 were intraspinal. Four of the 18 tumors were intra-axial (2 in the lateral ventricles and 2 within the spinal cord). Histologically, SFTs were similar to their soft tissue counterparts. Six tumors (6/18) had densely cellular regions, and 1 tumor showed frankly anaplastic features. All but 3 patients underwent gross total resection, and there were no metastases or tumor-related mortalities during the median follow-up of 40 months. In contrast, there were 15 local recurrences (83%), 5 extracranial metastases (27%), and 4 tumor-related deaths (22%) in the HPC cohort.
Conclusions.—Our study presents the clinicopathologic features of SFT as a distinct entity from both meningioma and HPC. We also present unusual examples of anaplastic, intraventricular, and intramedullary spinal SFTs that expand the clinicopathologic spectrum of these uncommon and sometimes diagnostically difficult neoplasms.
Two cases of nasal tumors with pericytic myoid differentiation are reported. The tumors occurred in a 77-year-old woman and a 60-year-old man as polypoid lesions covered by normal mucosa. Histologically, the tumors were composed of uniform short spindle or stellate cells with indistinct cell borders arranged in narrow and short fascicles. Numerous blood vessels of various sizes were common in both cases. The tumor cells of both cases stained intensely with anti-vimentin and anti-actin antibodies, but not with anti-desmin, CD34, or anti–high-molecular-weight caldesmon antibodies. Ultrastructural examination revealed well-developed actin thin filaments with dense bodies, subplasmalemmal plaques, intercellular junctions, and irregular discontinuous basement membranes. These histopathologic features suggest true pericytic differentiation of the tumors (true hemangiopericytoma), unlike soft tissue–type hemangiopericytoma. Generally, sinonasal hemangiopericytomas are subdivided into soft tissue–type hemangiopericytomas and true hemangiopericytomas identical to the cases presented here. Soft tissue–type hemangiopericytomas are frequently highly aggressive, whereas true hemangiopericytomas show localized benign behavior. Sinonasal true hemangiopericytomas should be strictly differentiated from soft tissue–type hemangiopericytomas.
O13 (CD99) is a monoclonal antibody directed against the glycoprotein p30/32MIC2. which has been found to be a sensitive marker for Ewing’s sarcoma. The reactivity of O13 in spindle cell tumors has not been extensively investigated. We examined the reactivity of O13 in hemangiopericytoma (HPC), solitary fibrous tumor (SFT), synovial sarcoma (SS), meningioma, and malignant mesothelioma (10 sarcomatoid, 2 mixed). We found reactivity with 21 of 33 HPCs, 9 of 10 SFTs, 7 of 13 SSs, and 24 of 25 meningiomas: there was weak and focal staining in only 1 of 12 mesotheliomas. Staining intensity varied considerably but was strongest in meningiomas and weakest in mesotheliomas, Immunoreactivity for O13 clearly delineated the cytoplasmic membrane in meningothelial meningioma, was present in the long cytoplasmic processes of HPC and SFT, and was present predominantly in the cytoplasm of the spindled cells of SS. We conclude that O13 stains a wide variety of spindle cell tumors, often with a specific cytologic pattern.
A series of 106 cases of hemangiopericytoma was analyzed. The neoplasms occurred principally in adults (median age, 45 years), were deep seated, and were most common in the thigh (27 cases) and the pelvic retroperitoneum (26 cases). A painless mass was the first symptom in 96 of the patients. The median size of the excised tumors was 6.5 cm. Surgical removal of the tumor was often complicated by hemorrhage because of marked dilatation of the vascular bed in the vicinity of the neoplasm, probably as the result of rapid exchange of blood from the arterial to the venous circulation within the tumor. Microscopically, benign and malignant forms could be distinguished. The latter were characterized by increased cellularity, prominent mitotic activity, and foci of necrosis or hemorrhage. Follow-up information was obtained in 93 cases. Seventy-one of the 93 patients were living (two with recurrence and four with metastasis), and 22 had died (13 as the result of recurrence or metastasis and nine from unrelated causes). Recurrence preceded metastasis in more than two-thirds of the patients with evidence of metastasis. The 10 year survival rate was 70 per cent. The morphologic differences from other mesenchymal tumors showing a hemangiopericytoma-like vascular pattern are discussed, and the close resemblance of hemangiopericytoma to richly vascular forms of fibrous histiocytomas and synovial sarcoma is emphasized. Congenital or infantile hemangiopericytoma is described as a separate entity having a distinctive microscopic pattern and behavior.
Fourteen cases of a mediastinal neoplasm identical to solitary fibrous tumor (so-called fibrous mesothelioma) of the pleura were observed. The lesions presented with cough, chest pain, dyspnea, or as asymptomatic masses detected radiographically. Two patients had associated hypoglycemia. Eleven of the tumors were in the anterosuperior mediastinum. One arose on a pedicle from the thymus, and another had entrapped thymic elements. Tumor cells were variably immunoreactive for vimentin and actin, but not for keratin, and lacked ultrastructural evidence of mesothelial or epithelial differentiation. Eight cases had highly cellular mitotically active regions of which six of seven with follow-up behaved aggressively; the exception was the pedunculated tumor. A 13-cm, histologically bland tumor has recurred twice. Aggressive behavior was more common than reported for solitary fibrous tumor of the pleura, but the same criteria (size, cellularity, mitotic activity, presence of pedicle) were of prognostic significance. The occurrence of solitary fibrous tumor in the mediastinum with the suggestion of thymic origin for some cases, combined with the immunohistochemical and ultrastructural findings, support a mesenchymal origin for this tumor. The differential diagnosis includes spindle cell thymoma, hemangiopericytoma, and peripheral nerve tumors.
Sinonasal-type hemangiopericytoma is an uncommon upper aerodigestive tract tumor of uncertain cellular differentiation. We report 104 cases of sinonasal-type hemangiopericytoma diagnosed between 1970 and 1995 from the files of the Armed Forces Institute of Pathology. There were 57 females and 47 males ranging in age from 5 to 86 years (mean 62.6 years). The most common clinical presentation was airway obstruction (n = 57) and/or epistaxis (n = 54), with symptoms averaging 10 months in duration. The tumors involved the nasal cavity alone (n = 47) or also a paranasal sinus (n = 26), were polypoid, and measured an average of 3.1 cm. Histologically, the tumors were submucosal and unencapsulated and showed a diffuse growth with fascicular (n = 37) to solid (n = 50) to focally whorled (n = 7) patterns. The tumor cells were uniform in appearance with minimal pleomorphism and had spindle-shaped (n = 82) to round/oval (n = 18) nuclei with vesicular to hyperchromatic chromatin and eosinophilic to amphophilic to clear-appearing cytoplasm with indistinct cell borders. Multinucleated (tumor) giant cells were identified in a minority of cases (n = 5). Mitotic figures were inconspicuous and necrosis was absent. The tumors were richly vascularized, including staghorn-appearing vessels that characteristically had prominent perivascular hyalinization (n = 92). An associated inflammatory cell infiltrate that included mast cells and eosinophils was noted in the majority of cases (n = 87). The immunohistochemical profile included reactivity with vimentin (98%), smooth muscle actin (92%), muscle specific actin (77%), factor XIIIa (78%), and laminin (52%). Surgery was the treatment of choice for all of the patients; adjunctive radiotherapy was given to four patients. Recurrences developed in 18 patients within 1–12 years from diagnosis. Ninety-seven patients were either alive (n = 51, mean 16.5 years) or dead (n = 46, mean 9.6 years) but free of disease. Four patients had disease at the last follow-up: three died with disease (mean 3.6 years) and one patient is alive with disease (28.3 years). Recurrent tumor (17.8%) can be managed by additional surgery. The majority of sinonasal-type hemangiopericytomas behave in a benign manner with excellent long-term prognosis (88% raw 5-year survival) following surgery alone. Sinonasal-type hemangiopericytomas have a characteristic light microscopic appearance with an immunophenotypic profile resembling that of glomus tumors. Almost from its initial description by Stout and Murray as a tumor primarily composed of pericytic cells, 42 the diagnosis of hemangiopericytoma (HPC) as a specific tumor type has been questioned. This skepticism has been predicated on the absence of any differentiating features by light microscopy coupled with the fact that the diagnosis of HPC often rests on its architectural features, specifically the presence of ramifying or branching pattern of its vascular component. However, this “specific” vascular pattern is found in a wide array of neoplasms of divergent differentiation such that a diagnosis of HPC is made only after excluding other tumors with similar histologic features. To the argument that HPC does not exist as an independent entity 15 comes the identification of the solitary fibrous tumor (SFT), a tumor originally described as a pleural-based tumor but now known to occur throughout the body. 19,23,43 Solitary fibrous tumor shares a perivascular pattern and CD34-positive tumor cells with HPC, suggesting common cellular differentiation between these tumor types. The questionable existence of soft tissue HPC as a specific entity is similarly posed relative to sinonasal tract HPC. The reasons for this skepticism are multifactorial, not the least of which include differences in the light microscopic features and overall biologic behavior between these sinonasal tract lesions and soft tissue HPC. As a result, the specific direction of differentiation for the sinonasal tract HPCs is still uncertain as attested to by the “hemangiopericytoma-like” designation with the implication that these tumors are related yet distinct from soft tissue HPC. 8 We undertook this study in an attempt to clarify some of the controversial issues surrounding the sinonasal-type HPC, specifically trying to suggest its possible link to other perivascular lesions. As we will discuss, our preferred terminology for this tumor is sinonasal-type hemangiopericytoma (SNTHPC).
The clinicopathologic features of 24 tumors showing perivascular myoid differentiation are described. These included tumors with histologic features of "infantile-type" myofibromatosis occurring in adult patients (8 cases), tumors with composite features of "hemangiopericytoma" and glomus tumor (9 cases), and tumors with a distinctive concentric perivascular proliferation of spindle cells (7 cases). Evidence of morphologic overlap among these groups suggests they are closely related neoplasms that form a single spectrum. Age of patients with lesions resembling infantile-type myofibromatosis ranged from 23 to 67 years (median, 37 years). Clinicopathologic manifestations of this disease included multicentricity (4 cases), local recurrence (3 cases), persistence of congenital lesions into adulthood (4 cases), and tumors that were multifocal within the confines of one anatomic region (7 cases). Histologically, all cases showed a biphasic pattern that consisted of fascicles of spindle cells with abundant eosinophilic cytoplasm that resembled smooth muscle, in addition to a population of more primitive spindled cells associated with a hemangiopericytomalike vascular pattern. Six cases showed reversal of the typical zonation seen in pediatric cases in that the primitive component surrounded the more mature fascicular areas. Also described are nine tumors with features that are intermediate between glomus tumor and hemangiopericytoma, which we have designated glomangiopericytoma. These tumors are characterized by prominent branching vessels lined by a single row of endothelial cells surrounded by epithelioid cells with a glomoid appearance. In other areas, the tumors showed typical hemangiopericytomatous foci similar to those in the myofibromatosis cases. The principal points of distinction were a lack of myoid nodules and an absence of small primitive cells with basophilic cytoplasm. Ages of these patients ranged from 17 to 78 years (median, 35 years). All tumors were located in the subcutaneous tissue and the superficial soft tissue of the extremities. Recurrence developed in one of six patients with follow-up information. The recurrent tumor had features of angiomatoid malignant fibrous histiocytoma. Finally, we describe a subset of tumors characterized by concentric periluminal proliferation of bland, round to ovoid cells, which we have designated as myopericytoma. Patient age ranged from 10 to 66 years (median, 40 years). All were located in subcutaneous and superficial soft tissue of distal extremities. One patient had two recurrences in 3 years after initial excision. Our study suggests that these three lesional groups comprise a histologic continuum of tumors that share clinical similarities and that, perhaps, are designated more appropriately as perivascular myomas. The relationship of this family of tumors to so-called hemangiopericytoma is discussed.
A series of seven cases of a previously unrecognized potentially recurrent tumor occurring in the orbit of adult patients is reported. This lesion shows histologic appearances intermediate between, but distinct from, solitary fibrous tumor and giant cell fibroblastoma of soft tissue. Morphologically it is characterised by a richly vascularized, patternless spindle-cell proliferation containing pseudovascular spaces. Multinucleate giant cells (often of floret type) and cells with large, rounded nuclei are present both in the cellular areas and also lining the pseudovascular spaces. The stroma is variably collagenized or sometimes myxoid. Immunohistochemically, the tumor cells exhibit positivity for vimentin and CD34. Follow-up in five cases (median duration 24 months) revealed local recurrence in one patient and persistent tumor in another. The clinical and morphologic features enable distinction of this lesion from both solitary fibrous tumor and giant cell fibrobtoma, and we suggest the designation "giant cell angiofibroma of the orbit".
We reviewed 223 localized fibrous tumors of the pleura and divided them histologically into 141 benign and 82 malignant neoplasms. The criteria used for a judgment of malignancy were high cellularity and mitotic activity (more than four mitotic figures per 10 high-power fields), pleomorphism, hemorrhage, and necrosis. The tumors occurred equally in both sexes, most commonly in the sixth to seventh decades of life. Presenting symptoms included chest pain, dyspnea, and cough; they were observed in three-fourths of patients with a malignant tumor. One in every four of these patients had hypoglycemia, clubbed digits, or pleural effusion. Two-thirds of the tumors were attached to visceral pleura, often by a pedicle. The rest arose from the parietal pleura of the chest wall, diaphragm, or mediastinum. Neoplasms in these atypical sites, together with fissural lesions and tumors "inverted" into peripheral lung, were more often malignant. Most neoplasms measured 5-10 cm and weighed 100-400 g. Microscopically, the "patternless pattern," or hemangiopericytic type, was seen in the majority of cases, and mixed patterns were seen in nearly 40% of tumors. Of the 169 tumors where follow-up was available, all of the benign and 45% of the malignant tumors were cured by simple excision. Patients surgically cured of a malignant neoplasm had pedunculated or well-circumscribed lesions. However, 55% of patients with malignant tumors succumbed to their disease secondary to invasion, recurrence, or metastasis. Resectability is the single most important indicator of clinical outcome. No tumor expressed epithelial differentiation, either immunohistochemically or ultrastructurally; therefore, we favor the term "localized fibrous tumor" of pleura instead of "localized mesothelioma."
Sinonasal hemangiopericytomas are rare, occasionally misdiagnosed neoplasms that have often been considered distinct from hemangiopericytomas of other sites. Eleven cases were studied. Nine arose from the nasal cavity and two from the paranasal sinuses. The patients' mean age was 58 years. In nine cases there were no appreciable mitoses; in two, mitoses were frequent. Of 10 cases studied by immunostaining, all were positive for vimentin; two had faint focal staining for actin; one focally expressed S-100 protein; all were negative for cytokeratins, desmin, and Factor VIII-related antigen; and none bound Ulex europaeus agglutinin 1. Five cases were studied by electron microscopy. The most consistent features were basal lamina-like material partly surrounding tumor cells and completely separating them from endothelium, tapered cytoplasmic extensions, and orderly bundles of filaments. Intercellular junctions and pinocytotic vesicles were present in some tumors. Of nine cases with adequate follow-up, tumors recurred in four cases (44%) after a mean of 6.5 years, and none metastasized. A review of the literature showed that high local recurrence rates, late recurrences, and low rates of metastasis were features of tumors in this location. This might be a reflection of early presentation, small tumor bulk, and difficulty of complete resection, rather than evidence for a biologically distinct neoplasm.
Haemangiopericytoma has been generally accepted for half a century as a distinctive histological type of soft tissue tumour. However, it has become apparent that many other types of tumour may closely mimic haemangiopericytoma, and that haemangiopericytoma itself shows, at best, only a limited morphological relationship to normal pericytes. Therefore this entire diagnostic concept has become controversial and requires reassessment: in particular there are no positive criteria by which to make this diagnosis, thereby bringing into doubt its very existence. With regard to the distinctive clinical and topographic subsets of haemangiopericytoma, there is good evidence that the infantile (or congenital) type represents the same entity as infantile myofibromatosis; the sinonasal type, which is almost always benign, appears to show evidence of myoid differentiation in some cases and may be more closely related to glomus tumour; the meningeal type, which was formerly misclassified as angioblastic meningioma, remains as difficult to categorise as the minority of soft tissue haemangiopericytomas which present in adulthood and which cannot easily be allocated to alternative diagnostic categories with more reproducible features.
A clinicopathologic study of 11 hemangiopericytomas is reported, and the results of clinical angiography in 4 patients and a correlated microangiographic-histologic study of 1 tumor are presented. Six of the tumors were collected and accepted as hemangiopericytomas in a review of 42 tumors registered as hemangiopericytoma in the Swedish Cancer Registry during the period 1958-1968. The other 5 tumors occurred in patients treated by us. The histologic examination and the follow-up information showed that it can be difficult to predict the prognosis on morphologic grounds, that borderline tumors exist and that a recurrence as well as a metastasis may dedifferentiate. The tumors studied by clinical angiography all proved to be highly vascular. Irregular vessels of varying caliber were filled with contrast medium and, in addition, a prominent diffuse opacification took place. Early filling of veins was not noted despite the high vascularity. The correlated microangiographic-histologic study suggests that the irregular vessels seen on clinical angiograms corresponded to wide, angulated, thin-walled vessels without muscle coat or elastic tissue, while the diffuse opacification was caused by a dense network of delicate, branching, slit-like capillary spaces. Cancer 42:2412–2427, 1978.
BACKGROUND
Solitary fibrous tumors (SFTs) are rare fibrous neoplasms. Since their initial description as arising from the pleura, SFTs have been reported at a wide range of anatomic sites. To the authors's knowledge, there are no large series reporting both thoracic and extrathoracic SFTs nor are there any large series that analyze clinicopathologic correlates of tumor behavior.METHODS
Institutional soft tissue tumor and pathology databases were reviewed to identify patients. Pathologic material was reviewed by an experienced soft tissue pathologist and scored for the presence of a histologically malignant component. Clinical information was obtained from medical records and phone calls to patients. Statistical analysis was performed using the Student t test, Pearson chi-square test, and log-rank test.RESULTSSeventy-nine patients with SFTs treated at a single institution over an 18-year period were identified. These tumors arose in a wide range of anatomic sites. Thoracic and extrathoracic SFTs had similar clinical and pathologic features, although extrathoracic tumors were more likely to be symptomatic on diagnosis. Seventy-five patients underwent surgical excision of a SFT at our institution. Overall, SFTs had a low rate of local recurrence and metastasis after surgical treatment. Extrathoracic SFTs had an increased risk of local recurrence that was small but statistically significant. There was no difference in metastasis-free survival between thoracic and extrathoracic SFTs. Positive surgical margins and the presence of a histologically malignant component were factors predicting worse local recurrence-free survival. Positive surgical margins, tumor size greater than 10 cm, and the presence of a malignant component predicted worse metastasis-free survival.CONCLUSIONS
Solitary fibrous tumors are rare tumors that occur at all anatomic sites. Most SFT patients fare well after surgical treatment. Closer surveillance is warranted for those tumors that are larger than 10 cm or with the presence of a histologically malignant component. Cancer 2002;94:1057–68. © 2002 American Cancer Society.DOI 10.1002/cncr.10328
A clinicopathologic study of 11 hemangiopericytomas is reported, and the results of clinical angiography in 4 patients and a correlated microangiographic-histologic study of 1 tumor are presented. Six of the tumors were collected and accepted as hemangiopericytomas in a review of 42 tumors registered as hemangiopericytoma in the Swedish Cancer Registry during the period 1958--1968. The other 5 tumors occurred in patients treated by us. The histologic examination and the follow-up information showed that it can be difficult to predict the prognosis on morphologic grounds, that borderline tumors exist and that a recurrence as well as a metastasis may dedifferentiate. The tumors studied by clinical angiography all proved to be highly vascular. Irregular vessels of varying caliber were filled with contrast medium and, in addition, a prominent diffuse opacification took place. Early filling of veins was not noted despite the high vascularity. The correlated microangiographic-histologic study suggests that the irregular vessels seen on clinical angiograms corresponded to wide, angulated, thin-walled vessels without muscle coat or elastic tissue, while the diffuse opacification was caused by a dense network of delicate, branching, slit-like capillary spaces.
The clinical, microscopic, and gross pathologic features of 23 cases of intranasal hemangiopericytoma-like tumors are reviewed and studied. When in the nasal cavity, these lesions often originated in a paranasal sinus and extended into the nasal cavity secondarily. They occurred most commonly in adults in the sixth and seventh decades of life; there was no significant sex predilection. Twenty-two of the 23 patients were Caucasian. These patients most commonly had symptoms of nasal obstruction and epistaxis. Clinically the lesions were generally thought to represent allergic polyps. Although appearing microscopically as non-differentiated spindle-cell neoplasms, these lesions showed little nuclear or cytoplasmic pleomorphism, minimal mitotic activity, and no necrosis or hemorrhage or other evidence of anaplasia found in malignant tumors. Follow-up data showed no evidence to suggest a malignant or biologically unpredictable lesion. Nineteen of 22 cases followed showed no recurrence regardless of the treatment; those that recurred did so locally. No metastasis or other form of aggressive behavior attributed to hemangiopericytomas in other anatomic locations was seen in this series. Another case, diagnosed as a malignant hemangiopericytoma of the nasal cavity, showed dissimilar and anaplastic histologic features. This case metastasized and is discussed, though not included in this study.
A series of 106 cases of hemangiopericytoma was analyzed. The neoplasms occurred principally in adults (median age, 45 years), were deep seated, and were most common in the thigh (27 cases) and the pelvic retroperitoneum (26 cases). A painless mass was the first symptom in 96 of the patients. The median size of the excised tumors was 6.5 cm. Surgical removal of the tumor was often complicated by hemorrhage because of marked dilatation of the vascular bed in the vicinity of the neoplasm, probably as the result of rapid exchange of blood from the arterial to the venous circulation within the tumor. Microscopically, benign and malignant forms could be distinguished. The latter were characterized by increased cellularity, prominent mitotic activity, and foci of necrosis or hemorrhage. Follow-up information was obtained in 93 cases. Seventy-one of the 93 patients were living (two with recurrence and four with metastasis), and 22 had died (13 as the result of recurrence or metastasis in more than two-thirds of the related causes). Recurrence preceded metastasis in more than two-thirds of the patients with evidence of metastasis. The 10 year survival rate was 70 per cent. The morphologic differences from other mesenchymal tumors showing a hemangiopericytoma-like vascular pattern are discussed, and the close resemblance of hemangiopericytoma to richly vascular forms of fibrous histiocytomas and synovial sarcoma is emphasized. Congenital or infantile hemangiopericytoma is described as a separate entity having a distinctive microscopic pattern and behavior.
Normal pericytes were found to express factor XIIIa (F-XIII) and histocompatibility antigen HLA-DR. These markers were studied in 15 hemangiopericytomas (HPC) and 16 other tumors with an HPC-like pattern. A subpopulation of tumor cells expressing F-XIII and HLA-DR antigens was a constant feature of HPC and supported their pericytic origin. Meningeal HPC did not differ in phenotype from peripheral soft tissue HPC. Most tumors with an HPC-like pattern (including synovial sarcomas, malignant schwannomas, leiomyosarcomas, and liposarcomas) were negative for F-XIII and HLA-DR. Malignant fibrous histiocytomas, however, invariably contained a subpopulation expressing these antigens. Therefore, F-XIII can be considered as a marker of fibrohistiocytic differentiation in HPC. Individual tumor cells in HPC occasionally were positive for factor VIII-related antigen (F-VIII-R-Ag), suggesting that the spectrum of differentiation in HPC may include the endothelial cell line. The differentiation characteristics of HPC support the concept that pericytes are primitive cells that may act as precursors to other mesenchymal cells.
• The clinicopathologic and the flow cytometric DNA characteristics of 14 patients with sinonasal hemangiopericytomas are presented. Patient and tumor characteristics were similar to previously published series. Flow cytometric analysis revealed a diploid DNA pattern and low S-phase in 13 neoplasms and an aneuploid DNA pattern with relatively high S-phase in one. Histopathologically, all diploid and low S-phase neoplasms displayed relatively uniform cellular features and low mitotic counts. All patients are alive and free of disease; one is still alive after a single recurrence. Our data suggest that sinonasal hemangiopericytomas are low-grade neoplasms as evidenced by their histomorphology and their DNA content. Recurrences are delayed and can be controlled.
(Arch Otolaryngol Head Neck Surg. 1992;118:134-137)
A review of the histologic growth patterns in 50 cases of benign and malignant fibrous tumors of the pleura (localized or solitary fibrous tumor, fibrous mesothelioma) is presented. Two major histologic growth patterns were observed admixed in various proportions: solid spindle and diffuse sclerosing. The solid spindle growth pattern assumed various configurations, including fascicular areas, storiform and herringbone formations, angiofibroma and hemangiopericytoma-like areas, synovial sarcoma-like areas, and neural-type palisading, thus simulating a variety of soft-tissue neoplasms. The diffuse sclerosing pattern, although rarely assuming a dominant role, was present in varying proportions in virtually all cases. In areas with extensive sclerosis, focal degeneration of collagen simulating tumor necrosis was often present. Other less frequently observed features were the formation of "amianthoid" fibers, multinucleated giant cells, and foci of metaplastic ossification. On ultrastructural and immunohistochemical examination, the tumor cells showed nondistinct features. Due to the extreme variability in morphologic appearances and the lack of distinctive ultrastructural or immunohistochemical characteristics, these tumors can pose a significant diagnostic problem. Familiarity with their histologic appearances and correlation with the gross findings and clinical setting are essential for arriving at the correct diagnosis.
Glomus tumors and hemangiopericytomas have traditionally been described as neoplasms of pericytes. Ultrastructurally, smooth muscle features have been identified in the cells of the glomus tumor, while the cells of the hemangiopericytoma have been described as more closely resembling normal pericytes. Immunocytochemical studies were performed to demonstrate the immunophenotype of these two tumors and to particularly evaluate expression of muscle-specific actin and desmin. Using the avidin-biotin immunoperoxidase method, formalin-fixed, paraffin-embedded tissue from 16 glomus tumors and 11 hemangiopericytomas was evaluated for the presence of vimentin, low-molecular-weight cytokeratins (35 beta H11), muscle actins (HHF35), desmin (clone 33), S100 protein, nerve growth factor receptor (NGFR5), myelin-associated glycoprotein (CD57), Factor VIII-related antigen, and Ulex lectin. Muscle actins were found in 14 of 16 tumors, and desmin was found in three of 16 of the glomus tumors. None of the 11 hemangiopericytomas expressed either desmin or muscle actins. Variable numbers of both tumors were positive with antibodies to CD57, with the nerve growth factor receptor, and with antibodies to S100 protein. In conclusion, these studies provide immunocytochemical evidence of smooth muscle differentiation in glomus tumors. Although muscle differentiation has been identified in the normal pericyte by expression of muscle-specific actin (HHF35), we find no evidence for analogous differentiation in the population of cells comprising hemangiopericytomas.
The debate on the nosologic position of hemangiopericytomas of the meninges has been based mainly on light microscopic and ultrastructural considerations; recent immunohistochemical studies have yielded controversial results. We have used a panel of antibodies to vimentin, desmin, actin, S100 protein, epithelial membrane antigen, cytokeratins, Leu-7, factor VIII-related antigen and type IV collagen to compare the immunophenotype of 10 soft-tissue and seven meningeal hemangiopericytomas. The immunophenotypic profile of these tumors is identical, and differs from that of meningiomas in that epithelial membrane antigen and cytokeratin are not present. The vascular pattern occurring in some meningiomas can simulate true hemangiopericytomas of the meninges. Immunohistochemical studies should allow their distinction in each instance. Meningeal and soft-tissue hemangiopericytomas display similar ultrastructural features.
Sinonasal hemangiopericytomas are rare, occasionally misdiagnosed neoplasms that have often been considered distinct from hemangiopericytomas of other sites. Eleven cases were studied. Nine arose from the nasal cavity and two from the paranasal sinuses. The patients' mean age was 58 years. In nine cases there were no appreciable mitoses; in two, mitoses were frequent. Of 10 cases studied by immunostaining, all were positive for vimentin; two had faint focal staining for actin; one focally expressed S-100 protein; all were negative for cytokeratins, desmin, and Factor VIII-related antigen; and none bound Ulex europaeus agglutinin 1. Five cases were studied by electron microscopy. The most consistent features were basal lamina-like material partly surrounding tumor cells and completely separating them from endothelium, tapered cytoplasmic extensions, and orderly bundles of filaments. Intercellular junctions and pinocytotic vesicles were present in some tumors. Of nine cases with adequate follow-up, tumors recurred in four cases (44%) after a mean of 6.5 years, and none metastasized. A review of the literature showed that high local recurrence rates, late recurrences, and low rates of metastasis were features of tumors in this location. This might be a reflection of early presentation, small tumor bulk, and difficulty of complete resection, rather than evidence for a biologically distinct neoplasm.
We reviewed 223 localized fibrous tumors of the pleura and divided them histologically into 141 benign and 82 malignant neoplasms. The criteria used for a judgement of malignancy were high cellularity and mitotic activity (more than four mitotic figures per 10 high-power fields), pleomorphism, hemorrhage, and necrosis. The tumors occurred equally in both sexes, most commonly in the sixth to seventh decades of life. Presenting symptoms included chest pain, dyspnea, and cough; they were observed in three-fourths of patients with a malignant tumor. One in every four of these patients had hypoglycemia, clubbed digits, or pleural effusion. Two-thirds of the tumors were attached to visceral pleura, often by a pedicle. The rest arose from the parietal pleura of the chest wall, diaphragm, or mediastinum. Neoplasms in these atypical sites, together with fissural lesions and tumors "inverted" into peripheral lung, were more often malignant. Most neoplasms measured 5-10 cm and weighed 100-400 g. Microscopically, the "patternless pattern," or hemangiopericytic type, was seen in the majority of cases, and mixed patterns were seen in nearly 40% of tumors. Of the 169 tumors where follow-up was available, all of the benign and 45% of the malignant tumors were cured by simple excision. Patients surgically cured of a malignant neoplasm had pedunculated or well-circumscribed lesions. However, 55% of patients with malignant tumors succumbed to their disease secondary to invasion, recurrence, or metastasis. Resectability is the single most important indicator of clinical outcome. No tumor expressed epithelial differentiation, either immunohistochemically or ultrastructurally; therefore, we favor the term "localized fibrous tumor" of pleura instead of "localized mesothelioma."
Since ultrastructural examination is often employed to assess controversial soft tissue tumors, it is important to be aware of the range of differentiation assumed by the tumor cells in hemangiopericytomas. For this purpose, 35 examples (10 localized to the central nervous system and 25 located peripherally) were examined ultrastructurally, and, of these, 20 cases were also studied immunohistochemically for the presence of intermediate filaments and muscle-specific actin. Based on cytologic characteristics evident by electron microscopy, tumor cell differentiation was classed as pericytic (32%), myoid (8%), nondescript (48%), fibroblastic (4%), and histiocytic (8%). Vimentin was the only intermediate filament expressed in the normal pericytes of human fetal and adult tissues and in the neoplastic pericytes of all of the hemangiopericytomas. Muscle-specific actin was present in normal pericytes, but only focally in two of the hemangiopericytomas. In various combinations basal lamina-like materials, cytoplasmic processes, cytoplasmic filaments, discrete basal lamina, and poorly formed intercellular junctions were the most frequently noted features of the tumor cells in hemangiopericytomas, whether central or peripheral, and they assist, along with the organizational relationship of tumor cells and capillaries, in distinguishing this lesion from other soft tissue sarcomas.
Fourteen cases of a mediastinal neoplasm identical to solitary fibrous tumor (so-called fibrous mesothelioma) of the pleura were observed. The lesions presented with cough, chest pain, dyspnea, or as asymptomatic masses detected radiographically. Two patients had associated hypoglycemia. Eleven of the tumors were in the antero-superior mediastinum. One arose on a pedicle from the thymus, and another had entrapped thymic elements. Tumor cells were variably immunoreactive for vimentin and actin, but not for keratin, and lacked ultrastructural evidence of mesothelial or epithelial differentiation. Eight cases had highly cellular mitotically active regions of which six of seven with follow-up behaved aggressively; the exception was the pedunculated tumor. A 13-cm, histologically bland tumor has recurred twice. Aggressive behavior was more common than reported for solitary fibrous tumor of the pleura, but the same criteria (size, cellularity, mitotic activity, presence of pedicle) were of prognostic significance. The occurrence of solitary fibrous tumor in the mediastinum with the suggestion of thymic origin for some cases, combined with the immunohistochemical and ultrastructural findings, support a mesenchymal origin for this tumor. The differential diagnosis includes spindle cell thymoma, hemangiopericytoma, and peripheral nerve tumors.
Five soft tissue hemangiopericytomas exhibiting the range of histologic types common to this tumor were studied with the electron microscope. Morphological correlates revealed that the better differentiated pericytes were present in the tumors or areas thereof displaying open capillaries, scant connective tissue, and oval, plump tumor cells. These findings support the concept of a pericytic histogenesis of this neoplasm. Well-differentiated pericytes were harder to find in areas with perivascular fibrosis and in tumors featuring spindle-shaped pericytes. Apparent forms of transition between pericytes and endothelial cells were common, especially in the less well-differentiated tumors. In one of these, atypical endothelial cells resembling those of endothelial sarcomas were present. These findings are suggestive of a close histogenetic relationship between hemangiopericytoma and hemangioendothelioma.
The clinical and pathologic features of 30 orbital hemangiopericytomas were reviewed. An effort was made to determine the clincopathologic characteristics that may correlate with the biologic behavior. Histopathologic criteria evaluated included degree of cellularity, nuclear atypia, mitotic activity, tumor size, and the presence of hemorrhage and necrosis. Histopathologically, 16 tumors were classified as benign, five as borderline, and nine as malignant. Follow-up information was obtained in 27 cases (mean duration of follow-up period was five and one-half years). Eight tumors recurred (30 per cent). Five patients died, four with widespread metastases (15 per cent) and one of unrelated causes. Tumors that recurred or metastasized were distributed among all three histologic groups. The interval between the onset of symptoms and metastasis for three of the four lethal tumors was 31 years, 28 years, and 8 1/2 years; in the fourth case it was unknown. For the entire series, the five-year actuarial survival rate was 89 per cent. Although the number of cases is too small to serve as a basis for firm conclusions, the lack of unequivocal correlation between the histologic features and clinical behavior is consistent with the unpredictable behavior of this neoplasm, as concluded by other investigators. Because of the apparent circumscription of most of these tumors, complete surgical excision rather than exenteration is recommended. Metastasis usually develops late in the clinical course of the disease, indicating that long-term follow-up studies are required before a cure can be assumed.
Three-hundred-sixty cases of solitary fibrous tumor of the pleura from the literature are analyzed, and eight new cases are described. Of patients reported on prior to 1972, 72% had symptoms due to the tumor at the time of diagnosis, but only 54% of patients reported on since then were symptomatic. This probably reflects earlier diagnosis as a result of increased use of chest radiographs in asymptomatic populations. Cough, chest pain, dyspnea, and/or pulmonary osteoarthropathy are each found in at least one-third of patients who have symptoms. Approximately 80% of solitary fibrous tumors of the pleura originate in the visceral and 20% in the parietal pleura. In the literature and in this experience these tumors are on the whole circumscribed. The range in size from 1-36 cm with a mean of 6 cm. Many are pedunculated on pleural-based pedicles that contain hypertrophic arteries and veins. Histologic examination of the tumor usually discloses cellular areas alternating with hyalinized and/or necrotic areas. Spindle-shaped cells typically have minimal nuclear pleomorphism and rare or absent mitoses. Numerous thin-walled vessels constitute an additional feature of large tumors. Electron microscopical examination reveals features of both fibroblasts and mesothelial cells. Solitary fibrous tumors behave in a benign fashion in 88% of cases after surgical resection. In 12% of the cases the tumor is responsible for the patient's death because of its extensive intrathoracic growth, by virtue of either late diagnosis or unresectable recurrence. No single histologic feature allows a definite prognosis. The best indicator of a good prognosis is the presence of a pedicle supporting the tumor. Also favorable in circumscription of the tumor without invasion of lung, mediastinum, or chest wall. Nuclear pleomorphism and a high mitotic rate are seen in larger tumors but do not necessarily indicate a poor prognosis if the tumor is circumscribed. Solitary fibrous tumors of the pleura are not associated with asbestos.
Solitary fibrous tumors are rare neoplasms that most commonly involve the pleura, mediastinum, and lung. Because they lack distinctive histologic features, immunologic staining has frequently been employed to exclude other neoplasms in the differential diagnosis. Their reported phenotype to date is generally negative, notably for muscle-type actins, desmin, keratin, and S-100 protein. Although this testing is of some help, it does not serve to distinguish all processes in the differential diagnosis, and when it does, it places too great an emphasis on a negative finding to make a diagnosis. We report here that CD34 monoclonal antibodies reacted with 11 of 14 solitary fibrous tumors in paraffin sections. Thus, they provide a positive marker that distinguishes the solitary fibrous tumor from most elements in the differential diagnosis.
A series of seven cases of a previously unrecognized potentially recurrent tumor occurring in the orbit of adult patients is reported. This lesion shows histologic appearances intermediate between, but distinct from, solitary fibrous tumor and giant cell fibroblastoma of soft tissue. Morphologically it is characterised by a richly vascularized, patternless spindle-cell proliferation containing pseudovascular spaces. Multinucleate giant cells (often of floret type) and cells with large, rounded nuclei are present both in the cellular areas and also lining the pseudovascular spaces. The stroma is variably collagenized or sometimes myxoid. Immunohistochemically, the tumor cells exhibit positivity for vimentin and CD34. Follow-up in five cases (median duration 24 months) revealed local recurrence in one patient and persistent tumor in another. The clinical and morphologic features enable distinction of this lesion from both solitary fibrous tumor and giant cell fibroblastoma, and we suggest the designation "giant cell angiofibroma of the orbit".
Twenty-nine tumors (from 26 patients, including two with recurrent disease) diagnosed as solitary fibrous tumor (SFT) of the pleura (n = 23), mediastinum (n = 4), abdominal cavity (n = 1), and parotid gland (n = 1) were studied immunohistochemically. Three histologically malignant tumors showed areas of high cellularity and mitotic activity (more than 4 mitoses/10 high-power fields) with features resembling malignant fibrous histiocytoma, malignant hemangiopericytoma, or fibrosarcoma, together with areas typical of benign solitary fibrous tumor. Formaldehyde-fixed, paraffin-embedded tissues and avidin-biotin-complex immunostaining were used. All of the tumors showed vimentin positivity and did not stain for cytokeratin, glial fibrillary acidic protein, or muscle cell markers, except for focal desmin reactivity in seven tumors, mostly seen in frozen sections, and focal keratin reactivity in one histologically malignant tumor. The neoplastic cells were positive for CD34 and negative for CD31; these patterns also were seen in the three histologically malignant cases. In nine of the cases acetone-fixed frozen sections showed variable focal positivity for neurofilament proteins of 68 kd. We conclude that SFT is a neoplasm of fibroblasts/primitive mesenchymal cells with features of multidirectional differentiation. We also report the finding of a novel site for SFT, the parotid gland.
Infantile myofibromatosis, congenital fibrosarcoma and congenital/infantile haemangiopericytoma are generally considered distinct entities. Overlapping microscopic features between infantile myofibromatosis and congenital fibrosarcoma, and between infantile myofibromatosis and congenital/infantile haemangiopericytoma, however, have been noted, but not formally reported. This report concerns six neonatal tumours, each exhibiting more than one of the above patterns, supporting a histogenetic relationship among these entities. Immunohistochemistry for smooth muscle actin was found to be useful in the diagnosis of congenital/infantile haemangiopericytoma, and also served to support a histogenetic relationship with the other two entities under consideration.
We report three cases of a unique, previously undescribed soft tissue tumor composed of mature adipocytes and hemangiopericytomatous areas, for which we propose the term lipomatous hemangiopericytoma. The tumors occurred in adults and were located in the sinonasal area, the soft tissue of the shoulder, and the retroperitoneum. The tumors ranged in size from 4 to 10 cm in greatest diameter and grossly were solid and ranged from tan to yellow. Histologically, they were composed of a variable admixture of benign lipomatous and hemangiopericytomatous components. Immunohistochemically, they stained with antibodies to vimentin and not to alpha-smooth-muscle actin, muscle-specific actin, desmin, S-100 protein, glial fibrillary acidic protein, epithelial membrane antigen, or keratin. Ultrastructurally, the cells constituting the hemangiopericytomatous areas had the features of pericytes, and no lipoblasts or transitional forms between lipocytes and pericytes were found. The histologic differential diagnosis of this neoplasm includes spindle-cell lipoma, angiolipoma, liposarcomas, tumors showing smooth muscle and adipocytic differentiation, and hemangiopericytoma infiltrating fat. Because of the small number of cases and the limited follow-up, we cannot be certain of their biologic behavior, although we expect that they are benign. Lipomatous hemangiopericytoma represents a distinctive pathologic entity that should be recognized and studied further.
The clinicopathologic features of 11 tumors, originally diagnosed as infantile hemangiopericytomas and with a spectrum of morphologic findings, are described. The age of the patients ranged from 6 days to 7 years; seven patients were younger than 1 year (mean, 2.25 years; median, 10 months); six were boys and five were girls. Three neoplasms were situated in skin or subcutis and seven in deep soft tissue; in one case the depth was unstated. Seven lesions arose in the lower limbs, and one each in the lumbar region, clitoris, chest wall, and soft tissue of the zygomatic region. One patient later was found to have two additional dermal tumors, one each on the anterior abdominal wall and the chest wall. Follow-up information in eight patients revealed local recurrence 12 years later in one case only. Histologically, all tumors showed distinctive features of infantile hemangiopericytoma, including immature cytology, multilobulated growth pattern, focal necrosis, and mitotic activity in varying degrees. Vascular invasion was noted in seven cases. Additionally, a second tumor cell component, composed of spindle-shaped myofibroblastic cells forming fascicles and micronodules, was evident at least focally. Both the spindle cells and more primitive round cells were positive for alpha-smooth muscle actin. Both cellular components showed a haphazard zoning arrangement. We discuss the clinicopathologic similarities between infantile hemangiopericytoma and infantile myofibromatosis and point out the differences between infantile and adult hemangiopericytoma. Our study suggests that there exists a broad spectrum of benign infantile myofibroblastic lesions containing an immature-appearing cellular component with a distinctive, hemangiopericytoma-like vascular pattern. Infantile myofibromatosis and so-called infantile hemangiopericytoma almost certainly represent different stages of maturation of the same (single) entity.
The tumor designated by Stout and Murray as 'hemangiopericytoma' (HPC) more than 50 years ago continues to represent a source of uncertainty end disagreement among pathologists. In particular, questions exist regarding the synonymity of a hemangiopericytomatous growth pattern-defined by a monomorphic population of compact polygonal or bluntly fusiform cells and a branching stromal vascular pattern with a 'staghorn' configuration-and the presence of a reproducible biological entity. It has been shown repeatedly that these same histologic features may be observed at least focally in a diversity of neoplasms, including 'true' hemangiopericytomas, synovial sarcomas, mesenchymal chondrosarcomas, infantile fibrosarcomas, malignant fibrous histiocytomas, malignant peripheral nerve sheath tumors, leiomyosarcomas, endometrial stromal sarcomas, solitary fibrous tumors, myofibromas, malignant mesotheliomas, thymomas, sarcomatoid carcinomas, malignant melanomas, and 'phosphaturic mesenchymal tumors.' Despite their potential sharing of the microscopic attributes in question, such neoplasms have individualistic clinical features and can also be distinguished from one another by specialized pathologic analyses. HPC is 'defined' in that context by reactivity for vimentin, with or without CD34 and CD57, but it lacks other immunodeterminants of epithelial, neural, and myogenous differentiation. Paradoxically, this phenotype is indeed associated with the presence of myogenous-type cytoplasmic filaments in ultrastructural evaluations of HPC. Other lesions that may resemble 'true' HPC-but which possess dissimilar subcellular end clinical characteristics-include solitary fibrous tumors, hemangiopericytomalike tumors of the sinonasal tract, and 'infantile (congenital) hemangiopericytomas.' Such observations suggest that the hemangiopericytoma is both a pathologic entity and a morphological pattern, and they emphasize the utility of adjuvant pathologic studies in this diagnostic context.