Giant cell tumors of tendon sheath. An electron microscopical study of 11 cases.

Light and electron microscopy of 11 giant cell tumors of tendon sheath revealed a pleomorphic cell population in which the giant cells had similarities to osteoclasts, and the stromal cells had similarities to primitive mesenchymal cells, osteoblasts, fibroblasts, and histiocytes. I suggest that giant cell tumors of tendon sheath are derived from mesenchymal cells with partial osseous differentiation.