HEMANGIOPERICYTOMA

Abstract
STOUT and Murray,1 in 1942, described a type of vascular tumor characterized by the formation of endothelial tubes and sprouts surrounded by closely packed, rounded and at times elongated cells. They demonstrated by tissue culture that these cells are derived from the capillary pericytes of Zimmerman2 and suggested hemangiopericytoma as a properly descriptive name. Various types of cells are closely applied to the outer surfaces of the capillaries, which in turn are composed of a single layer of endothelial cells. The pericapillary cells consist of connective tissue fibroblasts, histiocytes, mast cells, plasma cells, undifferentiated mesenchymal cells and in some instances an additional type of cell which has been called the Rouget cell and which, more recently, has been designated the pericyte. This contractile cell is spider-like, having numerous slender processes of a dendritic nature which encircle the capillary and serve to change the caliber of the lumen2