Bednar tumorBednar tumor is an eponym for pigmented variant of dermatofibrosarcoma protuberans (DFSP). It usually presents as a slow growing exophytic, multinodular subcutaneous mass arising on the trunk and, less frequently, on the extremities, head and neck of middle-aged adults. Bednar tumor (unlike conventional DFSP) appears to have strong predilection for blacks.
Microscopically, the tumor typically originates at the junction of the dermis and the subcutis. Epidermis appears normal and there is usually a layer of uninvolved dermis separating it from the tumor. The tumor itself is composed of spindle cells which resemble fibroblasts and are arranged in a storiform pattern. Cellular atypia is minimal and mitoses are rare. Necrosis is not a feature of Bednar tumor. The tumor is not demarcated and tends to infiltrate the subcutis in a charecteristic honeycomb pattern, spreading along the fibrous septa and sparing skin appendages.
The main feature distinguishing Bednar tumor from DFSP is the presence of the second population of pigmented melanin-containing dendritic cells.
Immunohistochemically, Bednar tumor stains diffusely positive for CD34. Characteristically, melanin-containing cells are typically negative for S-100.
Bednar tumor and DFSP are considered to be tumors of intermediate malignant potential. They can recur locally unless a wide excision margin is achieved, but rarely metastasize.