RESUMO
Benign fibrous histiocytoma [BFH] was microscopically similar to malignant fibrous histiocytoma [MFH] in their cellular population, secondary elements and their arrangement, however, the main difference was the absence of cellular atypia and the presence of conspicuous storiform pattern and necrosis. All malignant recorded cases were diagnosed as storiform-pleomorphic type, however, areas of myxoid changes, inflammation, mononucleated and multinucleated giant cells as well as areas of marked vascularity were often detected in these cases. Positive results for both immunohistochemical methods used with specific antibodies against HLA-DR antigens and S-100 proteins, were recognized as brown reaction products. Immunoreactivities of BFH and MFH for both antibodies were listed and the variability of the immunoreactivity of the cellular structures in all studied cases were also illustrated