Profiles of keratin proteins in basal and squamous cell carcinomas of the skin. An immunohistochemical study.

Profiles of immunohistochemical staining for different molecular weight keratin proteins (45, 46, 55, and 63 kilodalton (kd] were evaluated in basal and squamous cell carcinomas of the skin and surrounding epidermis. Basal cell carcinomas predominantly stained with antisera to low molecular weight keratins (45 and 46 kd). Staining with antisera to higher molecular weight keratins (55 and 63 kd) was focal and restricted to areas of squamous differentiation. Invasive squamous cell carcinomas in addition to staining with antisera to low molecular weight keratins (45 and 46 kd) showed diffuse staining for 55-kd keratin and foci of staining for 63-kd keratin most prominent in keratinized regions of the tumors. In situ squamous cell carcinomas (Bowen's disease) differed from invasive squamous cell carcinoma in showing increased staining for high molecular weight keratin (63 kd). Abnormal keratin profiles were identified adjacent to and overlying basal and squamous cell carcinomas, with antisera to low molecular weight keratins (45 and 46 kd) staining all layers of the epidermis, and decreased intensity of staining for high molecular weight keratin (63 kd). Keratin profiles may help define abnormal squamous maturation in epidermis adjacent to tumors. Immunohistochemical staining for different molecular weight keratin proteins may also be helpful in the differential diagnosis of skin lesions.