Localization of factor VIII/von Willebrand factor and glial fibrillary acidic protein in the hemangioblastoma: implications for stromal cell histogenesis.

The histogenesis of hemangioblastoma stromal cells is unresolved. Ultrastructural observations suggest that the stromal cells, endothelial cells, and pericytes that compose this neoplasm are all derived from angiogenic mesenchyme. The expression of factor VIII/von Willebrand factor (FVIII/vWF), a specific marker for endothelial cells, and of glial fibrillary acidic protein (GFAP), a specific marker for glial cells, was examined in 16 hemangioblastomas using the peroxidase-antiperoxidase immunohistochemical method. Endothelial cell staining for FVIII/vWF was intense in 14 tumors, weak in one, and absent in another. There was no stromal cell staining in any of the neoplasms. Process-bearing, GFAP-positive cells were observed near the tumor margin in 13 cases, and deeper in the neoplasm in 8. In two of these tumors there were also occasional GFAP-positive cells that lacked processes and had a vacuolated cytoplasm. Virtually all of the GFAP-positive cells were interpreted as trapped astrocytes rather than stromal cells. The lack of expression of FVIII/vWF by the stromal cells indicates that they are antigenically distinct from endothelial cells. Several alternatives for stromal cell histogenesis remain open. The stromal undergone antigenic loss, or from angiogenic mesenchymal cells that do not express FVIII/vWF. Alternatively, the stromal cells may originate from non-angiogenic mesenchymal cells derived from the mesoderm or neuroectoderm.