Immunohistochemical profile of meningiomas and their histological subtypes.

Seventy-seven cases of meningioma (15 with single or multiple recurrences), selected on the basis of their histologic subtypes, and nine cases of neurilemoma were analyzed immunohistochemically for the presence of the five classes of intermediate filament proteins, neuron-specific enolase (NSE), protein S-100, epithelial membrane antigen (EMA), and HNK-1 (Leu-7). Most antibodies were studied with the alkaline phosphatase-antialkaline phosphatase method. The peroxidase-anti-peroxidase and avidin-biotin-complex methods were used for Leu-7 and NSE, respectively. Meningiomas were subdivided into groups showing cytokeratin or protein S-100 positivity. Coexpression of these two markers was rare (5%) and occurred in meningotheliomatous meningiomas only. Only in these cases was cytokeratin expression more frequent than in meningiomas taken together (33% versus 20%). In contrast, protein S-100 expression was less frequent (46% versus 60% on average). In fibrous meningiomas, both cytokeratins and NSE were expressed less frequently than on average (11% versus 20%, 67% versus 88%, respectively). Protein S-100 occurred in a higher percentage of cases. Transitional meningiomas did not show cytokeratin expression. Protein S-100 occurred in a higher percentage of cases. Transitional meningiomas did not show cytokeratin expression. Protein S-100 was expressed slightly more often than in the other subtypes. Psam-momatous meningiomas coexpressed more markers than any other subtype. Hemangioblastic and hemangiopericytic forms did not stain for EMA, but otherwise showed a staining profile similar to that of meningiomas. HNK-1 was expressed in 29% of meningiomas, particularly among tumors with anaplastic histologic features. There was no marker that retrospectively indicated impending recurrences.