Bednar tumor (pigmented dermatofibrosarcoma protuberans). An analysis of six cases.

Six cases of Bednar tumor were analyzed clinicopathologically along with a review of 39 published cases. The findings were then compared with data on 44 cases of ordinary dermatofibrosarcoma protuberans (DFSP) obtained from our files. The clinical manifestations of the patients and the anatomic locations of the tumors were similar between the two categories, but the rate of recurrence was lower in cases of Bednar tumor. The histologic pattern of Bednar tumor was indistinguishable from ordinary DFSP except for scattered melanosome-containing cells. Ultrastructural and immunohistochemical examinations showed no evidence of neuroectodermal differentiation of dominant spindle-shaped cells in Bednar tumor, supporting a fibroblastic line of differentiation. The origin and pathogenesis of the melanosome-containing cells were considered. These cells failed to react with HMB-45, a melanoma-specific antibody, and the large majority of melanosomes present were mature or at Stage IV, plus a few immature ones at Stage II. These pigmented cells do not appear to be neoplastic, and cannot be used as proof to indicate that Bednar tumor is a neuroectodermal neoplasm.