DIVERGENT DIFFERENTIATION IN PLEOMORPHIC XANTHOASTROCYTOMA - EVIDENCEFOR A NEURONAL ELEMENT AND POSSIBLE RELATIONSHIP TO GANGLION-CELL TUMORS

We report the detection of cytoplasmic immunoreactivity for neuronal/n euroendocrine antigens in a subpopulation of tumor cells within seven pleomorphic xanthoastrocytomas (PXAs). The expression of glial and neu ronal polypeptides was examined in routinely prepared surgical resecti ons by immunohistochemistry using well-characterized antibodies that r ecognize glial fibrillary acidic protein (GFAP), synaptophysin (SYN), and neurofilament triplet polypeptides (NFPs) in microwave-enhanced si ngle- and double-immunolabelling experiments. Each neoplasm contained cells that were immunoreactive for SYN and/or NFPs, GFAP, and occasion ally for both GFAP and either NFP or SYN. We conclude that abortive ne uronal/neuroendocrine differentiation may occur in PXAs, suggesting a relationship between PXA and other developmental neoplasms that reveal a more overt neuronal phenotype, such as ganglioglioma, dysembryoplas tic neuroepithelial tumor, and desmoplastic ganglioglioma, and with tu mors expressing ambiguous glial/neuronal lineage, such as the subepend ymal giant cell tumor of tuberous sclerosis. These findings suggest th at aberrant expression and accumulation of neuronal intermediate filam ents may account for the large, pleomorphic cell morphology observed i n many of these tumors.