Involucrin in squamous and basal cell carcinomas of the skin: an immunohistochemical study.

Involucrin is a precursor of cross-linked protein of human stratum corneum, and its appearance in the upper layers of the epidermis is a function of the normal differentiation of the keratinocyte. Cases of basal cell and squamous cell carcinoma were evaluated for the presence of involucrin using immunoperoxidase techniques on paraffin sections. Basal cell carcinomas were negative for involucrin with staining restricted to squamous horn cysts, while squamous cell carcinomas stained strongly, particularly in large keratinized cells. Cases of squamous cell carcinoma in situ (Bowen's disease) revealed increased staining for involucrin with staining of dyskeratotic cells at all levels in the epithelium. Abnormal patterns of staining were also noted in non-neoplastic epidermis adjacent to carcinomas. Immunohistochemical staining for involucrin identifying abnormal or premature keratinization is a sensitive marker for dyskeratosis in squamous epithelia and may have applications in the histopathologic evaluation of skin specimens.