Fibrohistiocytic differentiation in capillary hemangioblastoma.

Seven cases of capillary hemangioblastoma from the cerebellum and spinal cord were studied by immunohistochemical methods to determine the origin of the stromal cells. A subpopulation of factor XIIIa-positive tumor cells was a constant feature in hemangioblastomas. These stellate or spindle-shaped cells transformed into typical vacuolated stromal cells. Factor VIII-related antigen was limited to the vascular endothelium. Glial fibrillary acidic protein was present only in entrapped astrocytes. Staining for alpha-1-antitrypsin (alpha 1AT) and alpha-1-antichymotrypsin (alpha 1 ACT) was occasionally observed in stromal cells. It was concluded that the factor XIIIa-positive stromal cells in capillary hemangioblastoma indicate fibrohistiocytic differentiation, which is part of the differentiation spectrum of hemangiopericytomas.