Cutaneous horn of the penis: its association with squamous cell carcinoma and HPV-16 infection. Cutaneous horns of the penis are rare. Including this case, only 19 cases have been reported in the English-language literature. In 37% of the reported cases a malignant tumor was found beneath the cutaneous horn. Our case is remarkable because a stage I squamous cell carcinoma developed on the shaft of the penis of a neonatally circumcised man. Human genital carcinoma resulting from a multifactorial process in which "promoting" papillomavirus is an integral element is being increasingly reported. We review the relationship of circumcision to genital human papillomavirus infection and their synergism in the development of squamous cell carcinoma. 