Ultrastructure of cerebellar capillary hemangioblastoma. I. Weibel-Palade bodies and stromal cell histogenesis.

Ultrastructural study of three cases of cerebellar capillary hemangioblastoma demonstrated three major component cells: endothelial cells, pericytes and stromal cells. The stromal cells exhibited ultrastructural features reminiscent of the endothelial cells. Weibel-Palade bodies, cylindrical cytoplasmic organelles specific to endothelial cells, were found in the endothelial cells and stromal cells, but not in the pericytes. The finding supported the concept that stromal cells are closely related to endothelial cells and are likely derived from the angiogenic mesenchymal cells. Since von Willebrand protein has been shown to be concentrated in Weibel-Palade bodies, the finding of these bodies in the stromal cells provided a morphological evidence for the immunocytochemical expression of factor VIII/von Willebrand factor of the stromal cells in those cases in which it has been reported.