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- Doyle, Leona A., et al.
(author)
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Nuclear expression of STAT6 distinguishes solitary fibrous tumor from histologic mimics
- 2014
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In: Modern Pathology. - : Elsevier BV. - 1530-0285 .- 0893-3952. ; 27:3, s. 390-395
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Journal article (peer-reviewed)abstract
- Solitary fibrous tumor (SFT) is composed of spindled to ovoid cells in a patternless architecture with prominent stromal collagen and hemangiopericytoma-like vessels. Some tumors show hypercellularity, nuclear atypia, and significant mitotic activity; the latter feature in particular often portends an aggressive clinical course. SFT can sometimes be difficult to distinguish from other benign mesenchymal tumors and sarcomas. The most characteristic (albeit nonspecific) immunohistochemical finding in SFT is CD34 expression. A NAB2-STAT6 gene fusion, resulting in a chimeric protein in which a repressor domain of NGFI-A binding protein 2 (EGR1 binding protein 2) (NAB2) is replaced with a carboxy-terminal transactivation domain from signal transducer and activator of transcription 6, interleukin-4 induced (STAT6), was recently identified as a consistent finding in SFT. However, as these genes are located in close proximity on 12q13, this fusion can only rarely be detected by conventional chromosomal banding or fluorescence in situ hybridization analysis. Nuclear expression of the carboxy terminal part of STAT6 is a consistent finding in SFT of the meninges (so-called 'meningeal hemangiopericytoma'). We investigated STAT6 expression by immunohistochemistry in SFTs and other soft tissue tumors arising outside the central nervous system to validate the diagnostic utility of this novel marker. Whole-tissue sections of 231 tumors were evaluated, including 60 cases of SFT as well as other benign and malignant mesenchymal neoplasms and sarcomatoid mesotheliomas. Fifty-nine of 60 SFT cases (98%) showed nuclear expression of STAT6, which was usually diffuse and intense. All other tumor types were negative for STAT6, except for three dedifferentiated liposarcomas and one deep fibrous histiocytoma, which showed weak staining. In conclusion, STAT6 is a highly sensitive and almost perfectly specific immunohistochemical marker for SFT and can be helpful to distinguish this tumor type from histologic mimics.
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| 2. |
- Vivero, Marina, et al.
(author)
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GRIA2 is a novel diagnostic marker for solitary fibrous tumour identified through gene expression profiling
- 2014
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In: Histopathology. - : Wiley. - 0309-0167. ; 65:1, s. 71-80
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Journal article (peer-reviewed)abstract
- Aims: The NAB2-STAT6 fusion was recently identified as a consistent finding in solitary fibrous tumour (SFT), resulting in nuclear expression of the C-terminal part of STAT6. Gene expression studies of SFT revealed high expression of the GRIA2 gene. The aim of this study was to examine GRIA2 expression in SFTs and other soft tissue tumours to evaluate its diagnostic utility. Methods and results: Immunohistochemistry was performed on 375 soft tissue tumours. In total, 84 of 105 (80%) SFTs, including 86% of malignant SFTs and 100% of dedifferentiated SFTs, were positive for GRIA2. One SFT known to harbour the NAB2-STAT6 fusion but that was negative for STAT6 by immunohistochemistry was positive for GRIA2. It is of note that 93% of SFTs received in the last 3 years were positive for GRIA2, as compared with only 70% of older cases. The only other tumours that expressed GRIA2 were 15 of 20 (75%) cases of dermatofibrosarcoma protuberans (DFSP), four of nine (44%) myoepitheliomas, one synovial sarcoma (<1% of cells), and one schwannoma. Conclusions: GRIA2 is a useful marker for distinguishing SFT from most mimics. Among other CD34positive tumours, GRIA2 is also expressed in DFSP; however, clinical and histological features aid in their distinction. GRIA2 shows a limited distribution in other soft tissue tumours.
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