Immunohistochemical and ultrastructural studies of stromal cells in hemangioblastoma.

In order to shed more light on the controversial tissue histogenesis of the stromal cells (SC), light microscopic, immunohistochemical and electron microscopic studies were performed on surgical specimens of hemangioblastomas (36, 26 and 7 cases, respectively). SC were immunoreactive for vimentin, S-100 protein, and neuron specific enolase (NSE) in all cases. Occasional SC were also positive for desmin, smooth muscle actin, Factor VIII, Ulex europaeus lectin receptors, GFAP, and Factor XIIIa. However, majority of these cells were negative with all the endothelial and smooth muscle cell markers used. Electron microscopy demonstrated several different types of SC that were reminiscent of pericytes, smooth muscle cells and abnormal endothelium as well as the intermediate forms between all the above cell types. Few SC were found lining the vascular lumina. Some SC formed small cavities reminiscent of early capillaries. However, typical Weibel-Palade bodies were not found in these SC. It is concluded that SC represents a heterogeneous population of lipidized cells, derived predominantly from the vasogenic mesenchyme. Although immunohistochemistry failed to reveal any consistent antigenic property of SC, ultrastructural findings strongly support the hypothesis that these cells are modified or abnormally differentiated endothelial cells and pericytes.