No full-text available
To read the full-text of this research,
you can request a copy directly from the author.
Gastrointestinale Stromatumoren, Pathomorphologie und Molekularpathologie
Abstract
Gastointestinal stromal tumours (GIST) are the most common mesenchymal neoplasms of the digestive tract. They originate from the interstitial cells of Cajal. GIST are not regarded as benign tumours, and morphological risk assessment is generally recommended according to the NIH consensus adapted from Fletcher et al. Other classifications (Miettinen and Lasota, Joensuu) considering the tumour site and tumour integrity as individual criterion may give different assessment results. Therefore, a special note has to be given in a proper histopathological diagnosis, referring to the system of risk assessment used. The histological diagnosis of GIST requires immunohistochemistry (CD117, PDGFRα). In doing so the use of a panel of antibodies is recommended helpful to cover all differential diagnostic relevant possibilities of mesenchymal neoplasms of the digestive tract. Analysis of the hot spot regions of KIT and PDGFRα genes is important for therapy planning and also may have some prognostic significance, for which reason it is recommended to be performed in GIST regularly.
Gastrointestinal stromal tumors (GIST) are the most frequent mesenchymal tumors of the gastrointestinal tract. The standard therapy is complete surgical resection with safety margins of 1-2 cm. Intraoperative rupture of the tumor capsule must be avoided because this carries a very high risk of tumor spread. A lymph node dissection is not routinely indicated as lymph node metastases very rarely occur with GIST. Smaller GISTs can normally be removed laparoscopically according to the rules of tumor surgery. Depending on the size of the tumor, the mitosis index and the localization of the primary tumor, the risk of recurrence after potentially curative resection is considerable in many cases. Patients with intermediate and high risks according to Miettinen's classification should receive adjuvant treatment with the tyrosine kinase inhibitor imatinib. Exceptions are those patients whose tumors exhibit the mutation D842V in exon18 of the PDGFRA gene. According to current European Society for Medical Oncology (ESMO) guidelines this therapy should be continued for 3 years. This leads to a significant improvement in progression-free survival compared to a 1-year therapy, and more important to an improvement in overall survival.
Podoplanin overexpression is associated with worse prognosis in several human cancers. In gastrointestinal stromal tumors (GISTs) very few data on the expression of podoplanin exist, but it seems to be frequently overexpressed in pediatric/syndromic GISTs. We investigated podoplanin expression and its clinical relevance in a large series of sporadic GISTs.
Podoplanin expression was determined immunohistochemically in 145 sporadic adult GISTs. Aneuploidies of 1p36 and 1q25 were investigated using FISH, and KIT and PDGFRA genes were investigated by sequencing.
Overexpression of podoplanin was observed in eight (5.6%) GISTs and no association with amplification of 1p36 or KIT or PDGFRA mutations was seen. The amount of podoplanin expression was not associated with clinical risk factors or patient survival.
Overexpression of podoplanin is a rare event in sporadic GISTs and is not associated with amplification of 1p36 or with KIT or PDGFRA mutations, which indicates limited pathobiological or clinical relevance.
The interstitial cells of Cajal (ICC) form a complex cell network within the gastrointestinal tract wall where they function as a pacemaker system. Expression of the kit proto-oncogene is essential for the development of this system. The aim of our study was to examine the hypothesis that gastrointestinal stromal tumors differentiate toward cells with an ICC phenotype. Ultrastructurally, 58 stromal tumors were characterized and found to share many features with ICC. Seventy-eight stromal tumors were immunophenotyped, particularly with regard to the kit receptor. All 78 tumors revealed strong, homogeneous immunoreactivity for the kit receptor as did ICC of adjacent and control gastrointestinal walls. Focal hyperplasia and hypertrophy of kit receptor positive cells were also observed in the gastrointestinal wall adjacent to the tumors. CD34 immunoreactivity observed in interstitial cells surrounding Auerbach's ganglia suggests that a subpopulation of ICC is CD34 positive and may explain why 56 of 78 stromal tumors were CD34 positive. Thirty control tumors, including gastrointestinal leiomyomas and leiomyosarcomas, were all negative for the kit receptor. We conclude that gastrointestinal stromal tumors show striking morphological and immunophenotypic similarities with ICC and that they may originate from stem cells that differentiate toward a pacemaker cell phenotype. We propose that the noncommittal name "gastrointestinal stromal tumor" be replaced by gastrointestinal pacemaker cell tumor.
As a result of major recent advances in understanding the biology of gastrointestinal stromal tumors (GISTs), specifically recognition of the central role of activating KIT mutations and associated KIT protein expression in these lesions, and the development of novel and effective therapy for GISTs using the receptor tyrosine kinase inhibitor STI-571, these tumors have become the focus of considerable attention by pathologists, clinicians, and patients. Stromal/mesenchymal tumors of the gastrointestinal tract have long been a source of confusion and controversy with regard to classification, line(s) of differentiation, and prognostication. Characterization of the KIT pathway and its phenotypic implications has helped to resolve some but not all of these issues. Given the now critical role of accurate and reproducible pathologic diagnosis in ensuring appropriate treatment for patients with GIST, the National Institutes of Health convened a GIST workshop in April 2001 with the goal of developing a consensus approach to diagnosis and morphologic prognostication. Key elements of the consensus, as described herein, are the defining role of KIT immunopositivity in diagnosis and a proposed scheme for estimating metastatic risk in these lesions, based on tumor size and mitotic count, recognizing that it is probably unwise to use the definitive term "benign" for any GIST, at least at the present time.
A mouse model of gastrointestinal stromal tumor (GIST) has been developed by a knock-in gene targeting strategy, which introduced a Kit gene K641E mutation, originally identified in sporadic human GISTs and in the germ line of familial GIST syndrome patients. Homozygous and heterozygous Kit K641E mice develop gastrointestinal pathology with complete penetrance and all Kit K641E homozygotes die by age 30 weeks due to gastrointestinal obstruction by hyperplastic interstitial cells of Cajal (ICC) or GISTs. Heterozygous mice have less extensive ICC hyperplasia and smaller GISTs, suggesting a dose-response relationship between oncogenically activated Kit and ICC proliferation. Immunoprecipitation and Western blotting reveal GISTs to contain abundant phosphorylated/activated Kit. In addition to ICC hyperplasia and GISTs, homozygous Kit K641E mice exhibit loss-of-function Kit phenotypes, including white coat color, decreased numbers of dermal mast cells, and sterility, indicating that despite its oncogenic activity the mutant form cannot accomplish many activities of the wild-type gene. Kit K641E reproduces the pathology associated with the familial GIST syndrome and thus is an excellent model to study Kit pathway activation, ICC biology, GIST pathogenesis, and preclinical validations of GIST therapies and mechanisms of drug resistance.
Oncogenic Kit mutations are found in somatic gastrointestinal (GI) stromal tumors (GISTs) and mastocytosis. A mouse model for the study of constitutive activation of Kit in oncogenesis has been produced by a knock-in strategy introducing a Kit exon 11-activating mutation into the mouse genome based on a mutation found in a case of human familial GIST syndrome. Heterozygous mutant KitV558Delta/+ mice develop symptoms of disease and eventually die from pathology in the GI tract. Patchy hyperplasia of Kit-positive cells is evident within the myenteric plexus of the entire GI tract. Neoplastic lesions indistinguishable from human GISTs were observed in the cecum of the mutant mice with high penetrance. In addition, mast cell numbers in the dorsal skin were increased. Therefore KitV558Delta/+ mice reproduce human familial GISTs, and they may be used as a model for the study of the role and mechanisms of Kit in neoplasia. Importantly, these results demonstrate that constitutive Kit signaling is critical and sufficient for induction of GIST and hyperplasia of interstitial cells of Cajal.
Context.—Gastrointestinal stromal tumors (GISTs) are specific, generally Kit (CD117)-positive, mesenchymal tumors of the gastrointestinal tract encompassing a majority of tumors previously considered gastrointestinal smooth muscle tumors. They are believed to originate from interstitial cells of Cajal or related stem cells.
Objective.—To review current clinicopathologically relevant information on GIST.
Data Sources.—Literature in Medline and authors' own experience.
Conclusions.—GISTs usually occur in older adults (median age 55–60 years) and rarely in children in the second decade (<1%) throughout the gastrointestinal tract: 60% in stomach, 35% in small intestine, and less than 5% in rectum, esophagus, omentum, and mesentery; most GISTs in the latter 2 sites are metastatic. Five percent of GISTs occur in patients with neurofibromatosis type 1 syndrome (multiple small intestinal tumors) and in Carney triad (gastric epithelioid GISTs in young females). Familial GISTs occur in patients with inheritable germline Kit or platelet-derived growth factor receptor alpha (PDGFRA) mutations. Histologically GISTs vary from spindle cell tumors to epithelioid and pleomorphic tumors. Most GISTs (95%) express Kit (CD117), CD34 (70%), and heavy caldesmon (80%), whereas 25% are positive for smooth muscle actin and less than 5% for desmin. Tumor size and mitotic activity are best predictive prognostic features; small intestinal tumors behave more aggressively than gastric tumors with similar parameters. Mutually exclusive gain-of-function Kit or PDGFRA mutations occur in a majority of GISTs representing in-frame deletions, point mutations, duplications and insertions. Mutations in Kit juxtamembrane domain (exon 11) are the most common in GISTs of all sites, whereas rare Kit extracellular domain (exon 9) Ala502-Tyr503 duplication is specific for intestinal GISTs. Mutations in PDGFRA have been identified in juxtamembrane (exon 12) and tyrosine kinase domains (exons 14 and 18), nearly exclusively in gastric GISTs, mostly in epithelioid variants. Some Kit and PDGFRA mutations have a prognostic value. Kit/PDGFRA tyrosine kinase inhibitor imatinib has been successfully used in the treatment of metastatic GISTs for more than 5 years. However, primary and acquired secondary resistance linked to certain types of Kit and PDGFRA mutations is limiting long-term success necessitating the use of alternative treatments.
As a result of major recent advances in understanding the biology of gastrointestinal stromal tumors (GIST), specifically recognition of the central role of activating KIT mutations and associated KIT protein expression in these lesions, and the development of novel and effective therapy for GISTs using the receptor tyrosine kinase inhibitor STI-571, these tumors have become the focus of considerable attention among pathologists, clinicians, and patients. Stromal/mesenchymal tumors of the gastrointestinal tract have long been a source of confusion and controversy with regard to classification, line(s) of differentiation, and prognostication. Characterization of the KIT pathway and its phenotypic implications has helped to resolve some but not all of these issues. Given the now critical role of accurate and reproducible pathologic diagnosis in ensuring appropriate treatment for patients with GIST, the National Institutes of Health (NIH) convened a GIST workshop in April 2001 with the goal of developing a consensus approach to diagnosis and morphologic prognostication. Key elements of the consensus, as described herein, are the defining role of KIT immunopositivity in diagnosis and a proposed scheme for estimating metastatic risk in these lesions, based on tumor size and mitotic count, recognizing that it is probably unwise to use the definitive term benign for any GIST, at least at the present time.
Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors in the gastrointestinal tract. Approximately 85% of GISTs harbor activating mutations in the KIT or platelet-derived growth factor receptor alpha (PDGFRA) gene and approximately 95% of GISTs are positive for KIT (CD117) by immunohistochemistry. Nevertheless, approximately 5% of GISTs lack KIT expression. Inhibition of KIT and PDGFRA by tyrosine kinase inhibitors has revolutionized the treatment of GISTs and demands accurate tumor classification. DOG1.1 is a recently described mouse monoclonal antibody reported to have superior sensitivity and specificity compared with KIT (CD117) and CD34. We evaluated this new antibody on a group of 81 GISTs obtained from 74 patients with special regard to KIT-negative GISTs (n=28), pediatric GISTs (n=11), and GISTs associated with neurofibromatosis type I (NF1) (n=16). Conventional GISTs (n=26) were also included. All conventional KIT-positive GISTs, all NF1-associated GISTs, and 9/11 pediatric GISTs expressed DOG1.1. DOG1.1 was expressed in 10/28 (36%) of KIT-negative tumors. The staining pattern was cytoplasmic and/or membranous. This study demonstrates that DOG1.1 is a sensitive immunohistochemical marker for GIST, comparable with KIT, with the additional benefit of detecting 36% of KIT-negative GISTs. DOG1.1 is also a sensitive marker for unusual GIST subgroups lacking KIT or PDGFRA mutations. In tumors that are negative for both KIT and DOG1.1, mutational screening may be required to confirm the diagnosis of GIST.
Accurate risk stratification of gastrointestinal stromal tumors (GISTs) has become increasingly important owing to emerging adjuvant systemic treatments. All GISTs have been considered to have some malignant potential, but this hypothesis is now seriously challenged by studies indicating that microscopic gastric GISTs that are common in the general population probably have little or no malignant potential. The National Institutes of Health (NIH) consensus classification system, based on tumor size and mitotic count, is commonly used to assess patient prognosis after surgical resection. Large retrospective cohort studies from several countries now uniformly indicate that the NIH classification carries substantial prognostic value. In particular, patients with high-risk GIST (approximately 44% of all) have substantially poorer outcome than those with intermediate-risk (24%) or low/very low-risk GIST (32%), whose survival is not markedly inferior to that of the general population in some studies. Gastric GISTs (approximately 58% of all GISTs) have a lower risk of recurrence than nongastric tumors of the same size and mitotic count, and tumor rupture confers clearly increased risk. These 2 important risk stratification factors are not considered in the NIH classification. Patients with certain nongastric tumors (2.1-5 cm and > 5 mitoses per 50 high-power fields or 5.1-10 cm and < or = 5 per 50 high-power fields) and those with tumor rupture are proposed to be included in the NIH high-risk category. High-risk patients defined by the proposed modified system have more than 15% to 20% risk of disease recurrence. The proposed system, if validated, may be useful in identifying which patients might potentially benefit from adjuvant therapy.
Interstitial cells of Cajal (ICCs) are believed to initiate the basic contractile activity of the gastrointestinal tract. Because ICCs in the intestine of mice express c-kit receptor tyrosine kinase and because rats are more commonly used than mice for pathophysiological investigations of the gastrointestinal tract, the number of the c-kit messenger RNA-expressing cells was compared with gastrointestinal movement in rats.
The c-kit messenger RNA-expressing cells were detected by in situ hybridization. The autonomous contraction of excised segments of the ileum was recorded. The function of the pyloric sphincter was evaluated by measuring the content of bile acids in the stomach.
The c-kit messenger RNA-expressing cells were not detectable in the stomach of Ws/Ws mutant rats with a small deletion at the tyrosine kinase domain of c-kit, and the number of c-kit messenger RNA-expressing cells decreased to 7% that of normal control rats in the ileum of Ws/Ws rats. The contractile activity of the ileum was apparently impaired, and the content of bile acids in the stomach was significantly increased in Ws/Ws rats.
The abnormalities in the ileal movement and pyloric sphincter function in Ws/Ws rats were attributable to the deficiency of c-kit messenger RNA-expressing cells.
Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors in the human digestive tract, but their molecular
etiology and cellular origin are unknown. Sequencing of c-kit complementary DNA, which encodes a proto-oncogenic receptor tyrosine kinase (KIT), from five GISTs revealed mutations in
the region between the transmembrane and tyrosine kinase domains. All of the corresponding mutant KIT proteins were constitutively
activated without the KIT ligand, stem cell factor (SCF). Stable transfection of the mutant c-kitcomplementary DNAs induced malignant transformation of Ba/F3 murine lymphoid cells, suggesting that the mutations contribute
to tumor development. GISTs may originate from the interstitial cells of Cajal (ICCs) because the development of ICCs is dependent
on the SCF-KIT interaction and because, like GISTs, these cells express both KIT and CD34.
Interstitial cells of Cajal (ICC) serve as pacemaker cells and mediators of neurotransmission from the enteric nervous system to gastrointestinal muscles. ICC develop from mesenchymal cells that express c-Kit, and signaling via Kit receptors is necessary for normal development of ICC. We studied the fate of functionally developed ICC after blockade of Kit receptors to determine whether ICC undergo cell death or whether the phenotype of the cells is modified. The fate of undeveloped ICC was also investigated.
Neutralizing, anti-Kit monoclonal antibody (ACK2) was administered to mice for 8 days after birth. ICC in the small intestine were examined by immunohistochemistry and electron microscopy. Occurrence of apoptosis was also assayed.
When Kit receptors were blocked, ICC nearly disappeared from the small intestine. Apoptosis was not detected in regions where ICC are normally distributed. Remaining Kit-immunopositive cells in the pacemaker region of the small intestine developed ultrastructural features similar to smooth muscle cells, including prominent filament bundles and expression of the muscle-specific intermediate filament protein, desmin, and smooth muscle myosin. ICC of the deep muscular plexus normally develop after birth in the mouse. Precursors of these cells remained in an undifferentiated state when Kit was blocked.
These data, along with previous studies showing that ICC in the pacemaker region of the small intestine and longitudinal muscle cells develop from the same Kit-immunopositive precursor cells, suggest inherent plasticity between the ICC and smooth muscle cells that is regulated by Kit-dependent cell signaling.
Extragastrointestinal stromal tumor (EGIST) is a unique tumor that occurs outside the gastrointestinal tract. EGIST shows a c-kit expression and histologic appearance similar to those of gastrointestinal stromal tumor (GIST). Most GISTs have gain-of-functional mutation of the c-kit gene, and some have mutation of the platelet-derived growth factor receptor-alpha (PDGFRA) gene. However, the frequency of mutation of those genes in EGISTs remains unclear. We examined the clinicopathologic features, prognostic factors, and c-kit and PDGFRA mutation in 39 cases of EGIST. Tumors with high mitotic counts (>or=5/50 high power fields) or a high Ki-67 labeling index (>or=10%) were significantly correlated with worse prognoses. The c-kit mutation was found in the juxtamembrane domain (exon 11) and the extracellular domain (exon 9) in 12 of 29 cases (41.4%) and 2 of 29 cases (6.9%), respectively. The PDGFRA gene mutation was found at the juxtamembrane domain (exon 12) and the tyrosine kinase domain (exon 18) in one case each. The pattern of kit and PDGFRA mutation in EGIST was essentially similar to that in GIST. Our results suggest that the c-kit and PDGFRA mutations play an important role in the tumorigenesis of EGIST. High mitotic counts and a high Ki-67 labeling index may be useful for predicting the aggressive biologic behavior in EGIST. Furthermore, STI-571, targeting c-kit and PDGFR tyrosine kinase, seems to be a possible therapeutic strategy for EGISTs, especially advanced cases.
Gastrointestinal stromal tumors (GIST) are a distinctive group of mesenchymal neoplasms of the gastrointestinal tract. The oncogene KIT has a central role in the pathogenesis of GIST, with c-kit receptor tyrosine kinase (KIT) protein expression being the gold standard in its diagnosis. The identification of GIST patients has become crucial, because the tyrosine kinase inhibitor Imatinib is effective in the treatment of this malignancy. However, a small set of GISTs remain unrecognized, because KIT protein expression is not always evident. The aim of this study was the identification of new markers for the differential diagnosis of GIST.
By analyzing publicly available data from transcriptional profiling of sarcomas, we found that protein kinase C theta (PKC-theta), a novel PKC isotype involved in T-cell activation, is highly and specifically expressed in GIST. PKC-theta expression in GIST was confirmed by reverse transcription-PCR and Western blot. PKC-theta was analyzed by immunohistochemistry in a panel of 26 GIST, 12 non-GIST soft-tissue sarcomas, and 35 tumors from other histologies.
We found that all of the GISTs expressed PKC-theta, whereas this protein was undetectable in other mesenchymal or epithelial tumors, including non-GIST KIT-positive tumors. PKC-theta immunoreactivity was also observed in interstitial cells of Cajal.
Our results show that PKC-theta is easily detected by immunohistochemistry in GIST specimens and that it could be a sensitive and specific marker for the diagnosis of this malignancy.
Gastrointestinal stromal tumors (GISTs) are specific, generally Kit (CD117)-positive, mesenchymal tumors of the gastrointestinal tract encompassing a majority of tumors previously considered gastrointestinal smooth muscle tumors. They are believed to originate from interstitial cells of Cajal or related stem cells.
To review current clinicopathologically relevant information on GIST.
Literature in Medline and authors' own experience.
GISTs usually occur in older adults (median age 55-60 years) and rarely in children in the second decade (<1%) throughout the gastrointestinal tract: 60% in stomach, 35% in small intestine, and less than 5% in rectum, esophagus, omentum, and mesentery; most GISTs in the latter 2 sites are metastatic. Five percent of GISTs occur in patients with neurofibromatosis type 1 syndrome (multiple small intestinal tumors) and in Carney triad (gastric epithelioid GISTs in young females). Familial GISTs occur in patients with inheritable germline Kit or platelet-derived growth factor receptor alpha (PDGFRA) mutations. Histologically GISTs vary from spindle cell tumors to epithelioid and pleomorphic tumors. Most GISTs (95%) express Kit (CD117), CD34 (70%), and heavy caldesmon (80%), whereas 25% are positive for smooth muscle actin and less than 5% for desmin. Tumor size and mitotic activity are best predictive prognostic features; small intestinal tumors behave more aggressively than gastric tumors with similar parameters. Mutually exclusive gain-of-function Kit or PDGFRA mutations occur in a majority of GISTs representing in-frame deletions, point mutations, duplications and insertions. Mutations in Kit juxtamembrane domain (exon 11) are the most common in GISTs of all sites, whereas rare Kit extracellular domain (exon 9) Ala502-Tyr503 duplication is specific for intestinal GISTs. Mutations in PDGFRA have been identified in juxtamembrane (exon 12) and tyrosine kinase domains (exons 14 and 18), nearly exclusively in gastric GISTs, mostly in epithelioid variants. Some Kit and PDGFRA mutations have a prognostic value. Kit/PDGFRA tyrosine kinase inhibitor imatinib has been successfully used in the treatment of metastatic GISTs for more than 5 years. However, primary and acquired secondary resistance linked to certain types of Kit and PDGFRA mutations is limiting long-term success necessitating the use of alternative treatments.