Hemangioendothelioma of the neuraxis: an ultrastructural study.

Hemangioendotheliomas are vascular tumors that rarely involve the neuraxis. However, when they do, they must be differentiated from the other neoplastic vascular lesions that more commonly involve the central nervous system (CNS). We describe the ultrastructural features of three hemangioendotheliomas of the neuraxis. These lesions are characterized by the proliferation of endothelial cells around vascular lumina and of pericytes outside of the endothelial basal lamina. These features differ from those of other vascular tumors of the CNS. Based on these observations, we consider hemangioendothelioma to be a distinct entity among the neoplasms of vascular origin in the CNS.