Basal cell carcinoma overlying a dermatofibroma

The epidermis over a dermatofibroma may show changes that range from simple hyperplasia to the proliferation of basaloid cells, which can become morphologically indistinguishable from basal cell carcinoma. The existence of a true basal cell carcinoma overlying a dermatofibroma is infrequent. These basaloid proliferations have usually been considered to be the result of the inductive effect of the fibrohistiocytic proliferation of the dermatofibroma on the epithelial cells of the hair follicle; therefore, it would be a reactive phenomenon and not truly neoplastic. We describe a case of dermatofibroma that presented with a basaloid proliferation identical in appearance to a basal cell carcinoma on the overlying epidermis.