MALIGNANT FIBROUS HISTIOCYTOMA

Malignant fibrous histiocytoma occurs less often in bone than in soft tissues. It usually presents as an aggressive stage IIB sarcoma; not infrequently, a pathologic fracture is the first clinical manifestation.

Diagnostic Studies. Radiographs show a destructive, radiolucent lesion with cortical erosion and a poorly defined, permeative margin. Extensive bony infiltration by the tumor occurs early in the course of the disease. When associated with a radiodense bone infarct, malignant fibrous histiocytoma may be misinterpreted as a sarcomatous transformation of enchondroma. Staging studies are used to define the extent of extraosseous involvement, and special attention should be directed to ruling out metastases to the regional lymph nodes as well as the chest.

The histologic pattern of malignant fibrous histiocytoma of bone resembles that of a poorly differentiated fibrous tumor. The tumor consists of histiocytic cells that secrete collagen lacking the herringbone pattern of fibrosarcoma. The appearance varies from reddish purple, friable neoplastic tissue to yellowish tan histiocytic tissue. The neoplastic areas are composed of large, bizarre, foamy histiocytes; malignant giant cells; and a loose storiform stroma of spindle cells. In addition, variable areas of necrosis, mitoses, and grossly abnormal histiocytes are present. The fibrous areas may suggest fibrosarcoma.

Treatment/Prognosis. An intraosseous stage IIB malignant fibrous histiocytoma requires resection with a wide margin. Chemotherapy is indicated with these lesions. The overall prognosis is fair.

FIBROSARCOMA OF BONE

Fibrosarcoma is a very rare lesion and usually presents as a painful, tender mass.

Diagnostic Studies. Radiographs reveal a poorly defined, destructive, radiolucent lesion of the metaphyseal region. These tumors are high grade and poorly marginated and produce a permeative, or “motheaten,” radiographic pattern of bone destruction.

Treatment/Prognosis. Fibrosarcomas require radical or wide margins with adjuvant chemotherapy. The prognosis for patients with stage II fibrosarcoma is fair.