Solitary fibrous tumors in the central nervous system: A clinicopathologic review of 18 cases and comparison to meningeal hemangiopericytomas
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. To define the clinicopathologic spectrum of SFTs in the central nervous system and to outline their differences from HPC and meningioma. We present the clinicopathologic features of 18 patients with SFT and compare them with those of an age- and sex-matched cohort of HPCs. 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. 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.
[Show abstract] [Hide abstract] ABSTRACT: Solitary fibrous tumors (SFT) are benign tumors of the soft tissue occurring anywhere in the human body but arise predominantly in the visceral pleura. SFT of the central nervous system are rare, especially when they occur within the spinal cord. We present a case of a 83 year old female patient presenting with acute spastic paralysis of the lower extremities after a history of progressive weakness and incontinence. MRI findings were typical for meningioma but an intradural, mainly intramedullary tumor was found at the first operation. A second operation was performed under neurophysiological monitoring and complete removal of the tumor was achieved. Neurological conditions improved after the procedure but the patient remained paraparetic. Histological and immunohistochemical findings revealed a SFT. There is evidence that SFT and HPC are not different entities but should be considered as different graduations of a common spectrum. The extent of resection is a prognostic factor for recurrence free survival in SFT, therefore we recommend surgery with complete resection whenever possible depending on the results of mandatory intraoperative neurophysiological monitoring in these cases. Copyright © 2015 Elsevier Inc. All rights reserved.0Comments 0Citations
- "Even though HPC is a rare tumor of the central nervous system, intramedullary occurrence has been described in a few cases (36). In contrast to SFTs, HPCs are typically hypercellular with a higher mitotic rate and presence of cell atypia, show CD34- positivity in 33%e100%, and are highly vascularized (5, 6, 16, 18, 25, 38). A cellular form of SFT that is indistinguishable from HPC has been described. "
[Show abstract] [Hide abstract] ABSTRACT: Non-central nervous system hemangiopericytoma (HPC) and solitary fibrous tumor (SFT) are considered by pathologists as two variants of a single tumor entity now subsumed under the entity SFT. Recent detection of frequent NAB2-STAT6 fusions in both, HPC and SFT, provided additional support for this view. On the other hand, current neuropathological practice still distinguishes between HPC and SFT. The present study set out to identify genes involved in the formation of meningeal HPC. We performed exome sequencing and detected the NAB2-STAT6 fusion in DNA of 8/10 meningeal HPC thereby providing evidence of close relationship of these tumors with peripheral SFT. Due to the considerable effort required for exome sequencing, we sought to explore surrogate markers for the NAB2-STAT6 fusion protein. We adopted the Duolink proximity ligation assay and demonstrated the presence of NAB2-STAT6 fusion protein in 17/17 HPC and the absence in 15/15 meningiomas. More practical, presence of the NAB2-STAT6 fusion protein resulted in a strong nuclear signal in STAT6 immunohistochemistry. The nuclear reallocation of STAT6 was detected in 35/37 meningeal HPC and 25/25 meningeal SFT but not in 87 meningiomas representing the most important differential diagnosis. Tissues not harboring the NAB2-STAT6 fusion protein presented with nuclear expression of NAB2 and cytoplasmic expression of STAT6 proteins. In conclusion, we provide strong evidence for meningeal HPC and SFT to constitute variants of a single entity which is defined by NAB2-STAT6 fusion. In addition, we demonstrate that this fusion can be rapidly detected by STAT6 immunohistochemistry which shows a consistent nuclear reallocation. This immunohistochemical assay may prove valuable for the differentiation of HPC and SFT from other mesenchymal neoplasms.0Comments 69Citations
- "In contrast , meningeal HPC have been shown to frequently recur locally and to metastasize. A direct comparison of age-and sex-matched SFT and HPC demonstrated a significantly higher count of mitoses in HPC, a significant higher incidence for local recurrence in HPC and a significantly higher incidence of metastases in HPC  . Such observations prompted the WHO classification of central nervous system tumors to foster a separate classification and allot the grades II and III to HPC. "
[Show abstract] [Hide abstract] ABSTRACT: A number of meningeal neoplastic lesions may radiologically and clinically simulate meningioma. In the present paper, we review meningeal non-meningothelial tumors which may also mimic different histotypes of meningioma at the histological examination. Awareness that these lesions exist may facilitate their recognition and correct diagnosis, which is of fundamental importance for prognosis and an appropriate therapeutic approach. Histological and immunohistochemical clues for the differential diagnosis are discussed.0Comments 3Citations
- "SFT, HPC and meningioma show overlapping radiological aspects . In addition, both SFT and meningioma present in the same age group and show a strong female predominance [15,63]. The typical histological features of SFT are spindle cells arranged in a pattern-less architecture or in interlacing fascicles, prominent collagenous bands and branching vascular channels with thin walls. "