Cells constituting cerebellar hemangioblastomas. Ultrastructural study.

Five capillary hemangioblastomas exhibiting a range of histologic variations common to this tumor were studied using electron microscopy. The capillary hemangioblastoma were composed commonly of three cell lines -- stromal cells, endothelial cells and pericytes. In addition, extramedullary hematopoietic foci were seen in the tissue of one case. We regarded all these cellular elements as neoplastic components. The interconvertibility among them was not confirmed. The capillary hemangioblastomas were highly organized by those multiple cell lines. The histologic pattern of growth was arbitrarily subgrouped into stromal cell prominent type and capillary prominent type. Intermediate features between the two types were observed. These different types would depend on relative proportions and the degree of maturity of the constituting cell elements. From the histogenetic point of view, we considered capillary hemangioblastomas as being a hamartomatous tumor.