Benign fibrous histiocytoma (Dermatofibroma) of the face - Clinicopathologic and immunohistochemical study of 34 cases associated with an aggressive clinical course

Thirty-four cases of fibrous histiocytoma (dermatofibroma) arising on the f ace are reported. These neoplasms occurred frequently in females (24 female , 10 male) and showed a broad age range (12 to 85 years; mean: 43.6 years, median: 41 years). The neoplasms originated on the forehead (nine cases), t he cheek (eight cases), the eyebrow (four cases), the temporal region (thre e cases), the nose (two cases), and the ear (one case); in seven cases the location face was given only. Five of 27 cases with follow-up information ( median: 5 years) recurred locally; in one case four recurrences were excise d within 8 years. The majority of cases extended into the subcutis and deep soft tissue including striated muscle (50% of cases). Histologically, only the minority of cases was composed entirely Of histiocytoid and spindle-sh aped tumor cells arranged in a storiform growth pattern. In many cases cell ular fascicles and bundles of spindle-shaped tumor cells were noted in addi tion to classical morphological features of fibrous histiocytoma. A moderat e mitotic rate (mean: 2.97 mitoses in 10 HPFs) was observed, and in few cas es increased atypia was evident. Frank tumor necrosis and/or vascular invas ion were not identified. Immunohistochemical studies revealed Factor XIIIa positivity in 13 out of 17, focal CD68 positivity in 6 out of 10, and alpha -smooth muscle actin positivity in 16 out of 19 cases tested. These lesions should be distinguished from dermatofibrosarcoma protuberans, including it s fibrosarcomatous variant, leiomyosarcoma, and low-grade myofibroblastic s arcoma. Cases of fibrous histiocytoma of the face have to be excised with w ider margins in comparison with examples of classical fibrous histiocytoma occurring on the extremities because of diffuse infiltration, involvement o f deeper structures, and an increased rate of local recurrences.