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Washington University Experience | NEOPLASMS (GLIAL) | Pleomorphic Xanthoastrocytoma (PXA) | 22H Case 22 Denouement
Comment: This case contains large pleomorphic (frequently multinucleated) cells, spindle cells, and lipidized cells but it lacks eosinophilic granular bodies. The tumor has a BRAF p.V600E mutation and homozygous CDKN2A and CDKN2B deletion. The report from the NIH DNA methylome analysis establishes this tumor as a pleomorphic xanthoastrocytoma (PXA). The report states “On methylation-based classification, tumors matching to this class display a much wider histologic spectrum compared to the original descriptions of this tumor type. On methylation profiling, pleomorphic xanthoastrocytoma represents an astrocytic tumor with varied histology, primarily that of pleomorphic xanthoastrocytoma or anaplastlc pleomorphic xanthoastrocytoma, but also including glioblastomas (particularly epithelioid glioblastoma) or with a ganglion cell-like differentiation appearing as 'anaplastic ganglioglioma'. There is no clear difference in methylation profiles between tumors histologically considered anaplastic or not. Location is typically supratentorial and often superficial (involving the leptomeninges). Most cases arise in teenagers or young adults, with median age at diagnosis around 20-25 years. Some tumors of this also display TERT promoter mutations, which may be associated with a poorer prognosis.” The presence of synaptophysin and other neuronal markers (e.g., NeuN, neurofilament) in a tumor with glial features (GFAP) is characteristic of PXA.
