Malignant fibrous histiocytoma. Evidence of perivascular mesenchymal cell origin immunocytochemical studies with monoclonal anti-MFH antibodies.

Using whole cell antigens prepared from the established lines of human malignant fibrous histiocytoma (MFH), the authors have generated two different monoclonal antibodies (FU3 and FU4) by a mouse hybridoma technique. By indirect immunoperoxidase in frozen tissue sections, FU3 and FU4 revealed strong staining of perivascular mesenchymal cells and fibroblasts. In the spleen FU3 stained perivascular cells of the ellipsoids and the marginal zone of the lymph follicles. Macrophages in granulation tissues as well as monocytes and other blood cells in normal peripheral blood were uniformly negative for the antigen detected by FU3. Among various soft-tissue tumors, MFH and liposarcoma reacted strongly with FU3 and FU4, but synovial sarcoma revealed no reaction with either of the antibodies. Immunoelectron-microscopic studies demonstrated positive reactions with FU3 and FU4 on the surface of MFH cell membrane, which suggests that these antibodies recognized cell surface antigens. In conclusion, MFH shares antigenicity with perivascular mesenchymal cells and fibroblasts as well as liposarcoma. MFH and liposarcoma may have a common origin from the perivascular mesenchymal cells that are supposed to have a potential for multidirectional differentiation.