Comparative study of p16 protein expression in squamous cell carcinomas from patients with epidermodysplasia verruciformis and patients without the disease

Epidermodysplasia verruciformis (EV) is a rare genodermatosis associated with susceptibility to beta-human papilloma virus (HPV) infection. EV patients develop disseminated warts and non-melanoma skin cancer, mainly squamous cell carcinomas (SCC) that are locally aggressive. EV pathogenesis is not yet fully understood, but alterations in the p16 gene play a role in the pathogenesis of neoplasms caused by high-risk genital HPV. To explore its role in EV lesions, we compared p16 expression in SCC from patients with and without EV. Tissue microarray slides composed of 27 SCC from EV patients, and 35 from non-EV patients were stained with an anti-p16 antibody. Twenty (74%) EV tumors exhibited diffuse (nuclear and cytoplasmic) p16 expression, one (4%) displayed focal expression, and six (22%) displayed no p16 staining. Eleven (31%) SCC from non-EV patients presented diffuse p16 staining, 14 (40%) displayed focal expression and 10 (29%) did not express p16. The frequency of diffuse p16 expression was higher in EV tumors than in SCC from patients without EV. The frequency of diffuse p16 expression in moderately and poorly differentiated EV-SCC was similarly higher than non-EV tumors with the same degree of differentiation. The diffuse expression of p16 in EV-SCC suggests that changes in the p16 gene, probably resulting in a functionally defective protein, may be one factor determining the locally aggressive clinical behavior of SCC in young EV patients.