Cell differentiation in benign cutaneous fibrous histiocytomas. An immunohistochemical study with antibodies to histiomonocytic cells and intermediate filament proteins.

Seven benign cutaneous fibrous histiocytomas (BFHs) were investigated immunohistochemically by using a panel of antibodies to histiomonocytic cells and intermediate filament proteins. Immunoreactivity with antimacrophage antibodies was observed in all tumors in a significant but varying proportion of the tumor cells. All tumors were also positive for vimentin. In addition, two of the BFHs were positive for cytokeratin and one for desmin. The results suggest that BFHs either display a true histiomonocytic trait or, alternatively, contain a prominent histiomonocytic infiltration. Some BFHs may be related to smooth muscle cells as indicated by desmin positivity. The occasional occurrence of cytokeratin in BFHs could also be explained by smooth muscle cell differentiation.