Hyperplastic cellular components of a hemangiopericytoma. An ultrastructural study

Abstract

Based on ultrastructural features of cellular components of a hemangiopericytoma, hyperplastic cells are classifiable into fibroblast-like (group 1), endotheloid (group 11) and pericyte-like (group 111) cells. The transformation of the group 1 cells to the group 11, or to the group 111 cells, is pronounced in our electron micrographs and this may imply that the group 1 cell is the principal cell of origin in this neoplasm. The smooth muscle-like (group IV) cells comprising the media of the arteries and veins in this neoplasm may represent modified, possibly de-differentiated smooth muscle cells reacted to the neoplastic proliferation of the surrounding adventitial (group 1) cells.