Importance of human papillomaviruses for the development of skin cancer.

The frequent detection of HPV DNA in non-melanoma skin cancers was shown in several studies; however, the role of HPV in the development of these cancers remains speculative. We analyzed different skin tumors, normal skin, and hair follicles for HPV DNA using a PCR system designed to detect all HPV types known so far. HPV DNA was found in 93% of common warts, 69% of squamous cell carcinomas (SCC), 52% of basal cell carcinomas (BCC), 41% of actinic keratoses, 31% of extragenital Bowen's disease, 22% of keratoacanthomas, 16% of normal skin tissues and 47% of hair follicles. No individual HPV type predominated in any of the skin tumors. The number of HPV genomes in individual neoplasms (SCC and BCC) seems to be less than I per cancer cell. These results indicate that a direct role of HPV in skin cancerogenesis remains questionable. Possibly, mechanisms different from the activity of HPV oncoproteins in genital cancers are involved in skin neoplastic transformation.