Distinctive Immunohistochemical Profile of Penile Intraepithelial Lesions: A Study of 74 Cases

Several classification schemes for penile precancerous lesions have been proposed, but none of them seems to correlate with the current understanding of penile cancer pathogenesis. Recently, a system, which takes into account morphologic features and purported etiopathogenesis, was proposed, separating penile intraepithelial neoplasia (PeIN) in differentiated and warty/basaloid subtypes. This study was designed to seek an immunohistochemical profile that can be helpful in the classification and differential diagnosis of penile epithelial abnormalities and precancerous lesions using the aforementioned system. The immunohistochemical panel included stains for p16, p53, and Ki-67. For p16 immunostaining, only full-thickness positivity in all epithelial cells was considered as positive; for p53 and Ki-67 immunostaining, patchy or diffuse nuclear positivity above the basal layer was considered as positive. Seventy-four lesions in 59 patients were selected and classified as follows: differentiated PeIN, 34 cases; squamous hyperplasia (SH), 21 cases; basaloid PeIN, 15 cases; and warty PeIN, 4 cases. The mean age of patients was 64 years. Forty-two lesions (56.8%) were located in the glans and 32 (43.2%) in the foreskin. Overexpression of p16 was useful for distinguishing SH from warty/basaloid PeINs (0% vs. 94.7%, P