Article
BRAF V600E immunohistochemistry in the diagnosis of Pleomorphic xanthoastrocyomas and Gangliogliomas
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Published: | September 11, 2012 |
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In the present study, we investigated a series of 33 PXA and 73 GG, as well as 29 Glioblastomas (GBM) and 13 supratentorial pilocytic astrocytomas (PA) as control cases by immunohistochemistry (IHC) using a previously described BRAF V600E mutation specific monoclonal antibody (clone VE1). VE1 specificity was verified by direct sequencing of BRAF in all cases. All cases of PXA and GG were additionally characterized for histological features and expression of other commonly used diagnostic markers (CD34, Synaptophysin and GFAP). VE1 immunohistochemistry was positive in 19/33 (58%) PXA, 41/73 (56%) GG, 0/29 (0%) GBM and 1/13 (8%) PA. DNA sequencing confirmed VE1 staining results in 100% of PXAs, 91% of GGs, 100% of GBMs and 100% of PAI. The morphological analysis of the series is currently ongoing. Preliminary results indicate that histological features are not markedly different between BRAF wild type and BRAF mutated tumors. Interestingly, GG that are supposed to represent well delineated lesion, presented with diffuse infiltration of VE1 positive ganglionic cells in several instances.
Our data confirm the high prevalence of BRAF (V600E) mutation in PXA and indicate that previously the BRAF mutation rate in GG was likely underestimated. Our data further substantiates the suitability of VE1 as an ancillary diagnostic marker in PXA and GG, especially for the differentiation of such lesions from other tumors like GBM or PA.