Cytokeratin Profile of Basal Cell Carcinomas According to the Degree of Sun Exposure and to the Anatomical Localization

Basal cell carcinoma (BCC) seems to originate from ultraviolet light-induced mutations involving the bulge or the outer sheath of the hair follicle cells. However, the etiopathogenic mechanisms involved in the development of these tumors in nonphotoexposed and in hairless areas remain unclear. The cytokeratin (CK) profile (including CK5/6, CK7, CK14, CK15, CK17, and CK19) from a series of different BCC subtypes developing in sun-exposed and non–sun-exposed areas, including hairless regions, was evaluated. The authors have observed that CK7 expression in BCC is associated with the anatomical localization of the tumor and its sun-exposition, but not with other factors such as histological subtype. The expression of this CK is higher in BCCs located in non–sun-exposed and nonhairy areas, such as the vulvar semimucosa and the nipple. Because CK7 is a marker of simple glandular epithelia, the authors suggest a glandular origin for BCCs located in hairless and nonphotoexposed areas.