Keratin Expression in Basal Cell Carcinomas

The study analyzed the keratin expression in 15 cases of basal cell carcinoma using immunohistochemistry. It found that the tumors strongly expressed primary keratins 5 and 14, typical of basal keratinocytes, but did not express secondary keratins 1 and 10, which are associated with skin differentiation. Keratin 17, linked to the outer hair root sheath, was consistently expressed in all tumors, while keratin 19, normally found in parts of the hair follicle, was present in four cases. Keratin 16, associated with high cell turnover, was often induced in the overlying epidermis but was rare in the tumor tissue. Simple epithelial keratins 8 and 18 were not expressed. The keratin profile of the tumor cells resembled that of basal cells in the hair root sheath, supporting the hypothesis of a follicular origin for basal cell carcinomas, but also suggested a potential origin from interfollicular pluripotent stem cells differentiating towards follicular structures.