Immunohistologic study of cellular populations of histiocytofibromas ("dermatofibromas").

Histiocytofibromas (HF) are benign tumours of the skin, the cellular composition of which is not yet known with certainty. The immunohistologic characteristics of 5 lesions were studied by using monoclonal antibodies and an indirect immunofluorescence method. All tumours were found to contain HLA-DR(+) cells, and, to a minor degree, OKM1(+) cells. OKT6(+) cells were present in the epidermis overlying the tumours; however in the HF themselves, no OKT6(+) cells were found. The presence of HLA-DR(+) and OKM1(+) cells demonstrates that HF contain cells bearing antigenic characteristics of histiocytes but not of Langerhans' cells, and we feel that the term "histiocytofibroma" is a more accurate designation for these lesions than "dermatofibroma".