Factor VIII related antigen and glial fibrillary acidic protein immunoreactivity in the differential diagnosis of central nervous system hemangioblastomas.

Nineteen hemangioblastomas, nine angioblastic meningiomas, ten metastases to the brain (including five renal cell carcinomas), and five primary renal cell carcinomas were studied using the immunoperoxidase method for Factor VIII related antigen and glial fibrillary acidic protein (GFAP). All tumor types showed Factor VIII immunoreactivity confined to endothelial cells. Factor VIII immunostaining revealed a distinct, though probably nondiagnostic, vascular pattern for hemangioblastomas as compared with metastatic carcinomas and angioblastic meningiomas. Most of the hemangioblastomas and metastases showed numerous GFAP-reactive cells with unequivocal astrocytic morphology primarily at the interface with brain parenchyma but also occasionally deep within the tumor. Within metastases these cells often were associated with penetrating fibrovascular septa. In a minority of hemangioblastomas and metastatic carcinomas there were rare GFAP immunoreactive cells that were indistinguishable from stromal or metastatic tumor cells, respectively. Angioblastic meningiomas showed no GFAP reactivity. It is concluded that the presence of GFAP-reactive cells alone is not helpful in differentiating between hemangioblastomas and intra-axial lesions. The lack of stromal cell immunoreactivity in angioblastic meningiomas and the rare staining of stromal cells in hemangioblastomas, seen also in central nervous system (CNS) metastases, suggest that except for the endothelial cells lining vessels, these primary CNS lesions are not antigenically closely related to either endothelial cells or astroglia. Furthermore, in the evaluation of tumors within the CNS, the significance of rare GFAP-positive tumor cells must be interpreted with caution.