Glial fibrillary acidic protein in stromal cells of some capillary hemangioblastomas: significance and possible implications of an immunoperoxidase study.

Thirty-nine hemangioblastomas from 26 patients were studied by the immunoperoxidase method for GFA protein. Reactive gliosis in the form of trapped GFA protein-positive astrocytes or astrocytic cell processes penetrated the margins of all the neuraxial tumors and none of those occurring on nerve roots or in the tumor explants maintained in an organ culture system. Gliosis was especially prominent in tumors recurring after surgical excision or in patients with a long history of tumor. In six tumors, representing both the reticular and the cellular variants of hemangioblastoma, GFA protein-positive stromal cells were also found, chiefly in the periphery of the neoplasma: all these tumors were surrounded by dense reactive gliosis. Four hypotheses accounting for the presence of GFA protein-positive stromal cells are considered: (1) The tumors are astrocytomas. (2) The GFA protein-positive cells are not neoplastic but lipidized or altered reactive astrocytes. (3) The tumors are mixed and partly composed of neoplastic astrocytes. (4) The stromal cells are capable of taking up extracellular GFA protein derived from the adjacent reactive astrocytes. The last of these hypotheses is the most consistent with the collective evidence derived from the histological findings. It implies that the presence of GFA protein in the cytoplasm of a cell does not necessarily establish that the cell is glial. The possibility of uptake of GFA protein by non-glial cells must be considered if dense gliosis is present in the vicinity.