A case of Bednar tumor. Immunohistochemical positivity for CD34.

A 42-year-old Japanese man with a Bednar tumor is described. The skin showed a slightly elevated, red, partially dark blue, dermal nodule growing into the deep subcutaneous tissue. The histological specimen showed two types of tumor cells, spindle-formed cells with no melanin granules and melanin-laden cells. Immunohistochemical stainings for CD34 and S-100 protein revealed that the former cells showed positivity only for CD34, while the latter were only positive for S-100 protein. These results suggest that the Bednar tumor is a dermatofibrosarcoma protuberans in which melanin-laden cells coexist.