Pigmented dermatofibrosarcoma protuberans with prominent meningothelial-like whorls.

Dermatofibrosarcoma protuberans (DFSP) is a locally aggressive skin tumor. In addition to the conventional type, several morphologic variants have been described. Recognition of these uncommon variants will facilitate the diagnosis. We report herein a peculiar case of pigmented DFSP (Bednar tumor) with prominent meningothelial-like whorls, a distinctive pattern that has not been described previously in DFSP. The tumor occurred in a 40-year-old man who presented with a slowly growing mass on his left shoulder. The overall histological features were consistent with Bednar tumor. However, unexpected numerous meningothelial-like whorls were found in some areas of the tumor. Like the tumor cells in typical areas of Bednar tumor these meningothelial-like whorls were also positive for CD34 but negative for epithelial membrane antigen and S100 protein. The meningothelial-like whorls in Bednar tumor represent an eccentric arrangement of the tumor cells. We propose the term 'pigmented DFSP with prominent meningothelial-like whorls' to highlight the distinctive pattern of this novel DFSP variant.