Ultrastructural features of malignant fibrous histiocytoma of bone.

Five cases of malignant fibrous histiocytoma originating in the femur and tibia, sometimes with local recurrences, are reported. Histological and clinical characteristics of this lesion were similar to those in soft tissues with the same disease. The present histiocytomas were observed by electron microscopy and shown to consist of 5 types of neoplastic cells which were regarded as undifferentiated cells, histiocyte-like cells, which were predominating, fibroblast-like cells, multinucleated giant cells and xanthomatous cells. These findings led us to confirm the existence of malignant fibrous histiocytoma originating in bone as well as in soft tissues.