Atypical fibroxanthoma of the skin. A clinico-pathological study of 57 cases

A retrospective study of 57 patients with atypical fibroxanthoma of the skin is presented. The light microscopy is described and the differential diagnosis is discussed. Most of the atypical fibroxanthomas (32 out of 57 cases) were originally diagnosed as soft tissue sarcomas, e.g. fibrosarcoma, dermatofibrosarcoma, neurofibrosarcoma, myosarcoma and unspecified sarcoma. The tumour occurred chiefly in middle-aged and elderly patients; three patients were 15 years old or younger. The median age was 73 years in patients in whom the tumour occurred in the head and neck, and 34 years in patients in whom the tumour developed on the extremities and trunk. The sex ratio (male to female) was almost equal. Follow-up information about 43 patients was available. The follow-up period ranged from 1 year to 25 years with a median of 9 years. Eight patients died from intercurrent disease; all the other 35 patients are alive and well. The clinical course was benign in all but one patient in whom a recurrence developed and metastases to the regional lymph nodes appeared 7 years after the initial excision. The tumour in this case did not differ histologically from the other atypical fibroxanthomas with respect to cellularity, cellular and nuclear atypia or mitotic activity. It is suggested that the recurrence per se might be of prognostic importance.