Histiocytoid endothelial cells in a malignant schwannoma.

Unusual vascular lining cells within a malignant schwannoma prompted a comparative study of these cells and the endothelial cells in cases of histiocytoid hemangiomas. The endothelial cells in all cases showed similar morphologic and immunohistochemical features. Such endothelial cells were not found in the capillaries of a pyogenic granuloma or in those of developing rat skin. It is postulated that these distinctive endothelial cells may be more widely distributed than was previously thought and that morphologic changes associated with these cells may be induced by vasoactive substances.