Basal Cell Carcinoma Arising within Seborrheic Keratosis.

Malignant tumour development within a seborrheic keratosis (SK) is extremely rare. Though the most commonly developed malignant tumour is the basal cell carcinoma (BCC), other tumour types have also been reported in literature. Herein, we will report a superficial type BCC case developed within SK localized in hairy skin of a 78-year-old female patient. In immunohistochemical evaluation, diffuse positive staining with CK19 and over-expression in p53 compared with non-neoplastic areas were determined in neoplastic basaloid islands. It is always not easy to differentiate especially superficial type BCC cases from non-neoplastic epithelium of SK with histopathological evaluation. As far as this reason we believe that in difficult differentiation of these 2 lesions, in order to show the differentiation in basal epithelium, immunohistochemical evaluation may be helpful.