Malignant giant cell tumor of soft parts. An ultrastructural study of four cases

Abstract

Four cases of malignant giant cell tumor of soft parts (MGCT) were studied ultrastructurally. Most of the cells in 3 patients were identified as undifferentiated mesenchymal cells and mononuclear monohistiocytic cells. The osteoclast-like cells seemed to arise from fusion of monohistiocytic cells. Immature fibroblastic cells, occasionally containing filaments with densities were also present. They were scarce in 3 cases and predominant in the 4th. MGCT is a mesenchymal sarcoma with a bimorphic monohistiocytic and fibroblastic differentiation. MGCT is considered a special variant of malignant fibrous histiocytoma.