Giant cell glioblastoma and pleomorphic xanthoastrocytoma show different immunohistochemical profiles for neuronal antigens and p53 but share reactivity for class III β-tubulin

Context. - Giant cell glioblastoma multiforme (GCGBM) and pleomorphic xanthoastrocytoma (PXA) are clinically, radiographically, and histologically distinct tumors of the central nervous system. However, they share features of gross circumscription, reticulin deposition, lymphocytic infiltrates, and prominent populations of tumor giant cells. Neuronal antigens have been detected in the neoplastic cells of PXAs, but to our knowledge have not been studied previously in GCGBMs. While TP53 is mutated in most GCGBMs, a feature usually paralleled by strong immunostaining of the protein, the expression pattern of PXAs has not been extensively studied. Objectives. - To compare the immunoprofiles of GCGBM and PXA with regard to neuronal antigens and p53 and to evaluate the potential diagnostic utility of such a panel. Design. - Archival paraffin sections of 9 GCGBMs and 9 PXAs were immunostained for class III β-tubulin, neuronal nuclear antigen, neurofilament protein, synaptophysin, glial fibrillary acidic protein, and p53. Results. - Giant cell glioblastomas were strongly immunoreactive for class III β-tubulin and glial fibrillary acidic protein, but showed only rare staining for the other neuronal polypeptides. In contrast, PXAs usually showed at least focal staining of individual tumor cells for most of the neuronal antigens tested. Tubulin was strongly positive in tumor giant cells and in smaller neoplastic cells of both tumor types. Double-immunolabeling revealed distinct populations of tumor cells that expressed either glial fibrillary acidic protein or tubulin and dual-labeling of individual cells in GCGBM and PXA. Strong p53 staining was observed in many tumor cells in 5 of 8 GCGBMs tested, while staining for this antigen was negative or focally positive in 6 of 8 PXAs examined. Conclusions. - Giant cell glioblastoma multiforme and PXA show distinct patterns of immunoreactivity for neuronal antigens and p53 that may be useful diagnostically in difficult cases or in limited samples. These results provide further evidence of neuronal antigen expression by PXA.