[Ultrastructure of experimental virus-induced hemangiopericytomas].

Electron-microscopy studies of malignant low-differentiated hemangiopericytomas, induced by adenovirus of monkeys SA7(C8) and bovine adenovirus type 3 were, carried out. At earlier stages of the development of these tumours in tumourous cells located around capillaries there were observed the ultrastructural characteristics typical of pericytes and cells of human hemangiopericytis: the presence of the basal layer and fibrills as thick as 40 A. As differentiation proceeded, tumorous cells acquired an elongated form, and in some of them there appeared myofilaments typical of smooth-muscle cells, with local thickenings, as well as multitude of pinicytic vacules along the plasmatic membranes of cells. The foregoing confirms the assumption of hemangiopericytomas as a prestage of leio-(angioleio-) myosarcomas. Moreover, the tumour cells revealed the presence of cilia, fibrills as thick as 100A, 75A, annulate lamelae, and myelin-like formations.