[Electron microscope study of pigmented villonodular synovitis].

The ultrastructure of pigmented villonodular synovitis was studied on the operation material from 5 patients. Differences in the cell composition of villous and nodular formations typical of the disease were found. Different functional conditions of foamy cells was noted. Since foamy and fibroblastic cells were most numerous the possibility of accumulation of mononuclear phagocytes capable of excreting a proliferation factor in response to the primary local disturbance of lipid metabolism in fibroblast cells in pigmented villonodular synovitis is discussed.