PCNA expression in cutaneous keratinous neoplasms and verruca vulgaris.

Using an antibody to PCNA and a standard immunohistochemical system, the authors examined normal epidermis and cutaneous neoplasias for expression of PCNA, a protein associated with DNA polymerase delta and DNA replication. In squamous cell carcinoma in situ (SCCI), a unique expression of PCNA, which frequently involved the nuclei of all keratinocytes within the lesion, was found. Heaviest staining was in the uppermost layers of the epidermis. PCNA expression ended abruptly at the histologic margin of the lesion. Because SCCI can be associated with the presence of human papillomavirus (HPV) DNA, the authors evaluated PCNA expression in verruca vulgaris and found a pattern similar to that in SCCI. Assuming that PCNA expression in these two lesions is related to cell division, the authors hypothesize that the mechanisms that control proliferation in SCCI may be similar to those operative in verruca vulgaris.