Pigmented dermatofibrosarcoma protuberans. Report of two cases as a variant of dermatofibrosarcoma protuberans with partial neural differentiation.

Two cases of so-called Bednár tumor are reported. The histopathological finding of a typical storiform pattern composed of fusiform tumor cells resembled dermatofibrosarcoma protuberans (DFSP) except for the presence of melanin-containing cells scattered within the lesion. Ultrastructurally, the predominant tumor cells in case 1 possessed extensive cytoplasmic processes, convoluted nuclei, and intercellular junctions, but lacked basal lamina. Melanocytic tumor cells contained melanosomes and were surrounded by basal lamina. Immunohistochemical examinations revealed a positive reaction for S-100 protein and neuron-specific enolase in the pigment-laden cells. Consequently, these two tumors were considered to be a variant of DFSP with partial neural differentiation.