Bednar tumor (pigmented dermatofibrosarcoma protuberans) occurring in a site of prior immunization: Immunochemical findings and therapy

Bednar tumor is a rare pigmented variant of dermatofibrosarcoma protuberans (DFSP). Because of its rarity, information is lacking regarding the optima l therapy and potential utility of immunohistochemistry in diagnosis. We re port a case of Bednar tumor in which the diagnosis was aided by immunohisto chemistry for CD34, an antigen known to be expressed in DFSP but not previo usly reported in Bednar tumor. Our case was also striking because it repres ents the first reported appearance of a Bednar tumor at a site of prior imm unization, a phenomenon previously noted in some cases of DFSP. The patient was treated effectively with Mohs surgery and is without recurrence at 9 m onths.