O. Inada

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, flbroblast‐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.

Naturally occurring angiosarcoma of the tibia in an NZB mouse.

An osteolytic bone tumor was found in a 12‐month‐old male NZB mouse. Macroscopically and histologically this tumor was angiosarcoma originating in bone with distant metastasis present in the spleen. The primary tumor was successfully transplanted in the back subcutaneous tissue of syngeneic mice, and the characteristics of the transplants, were found to be similar to those of the primary tumor. The ultrastructure of tumor is described.