[HPV type 16-associated anal intraepithelial neoplasia (AIN)].

A 25-year-old woman had suffered from a perianal ulcer for approximately 1 year. Topical and systemic treatments had been unsuccessful. Employing virologic and histologic techniques, we confirmed the diagnosis of an intraepithelial neoplasia. Anal intraepithelial neoplasia (AIN) is induced by carcinogenic human papillomaviruses. It can occur anywhere in the anogenital area. Because of its frequency, AIN is a crucial differential diagnosis for lesions of the anogenital area region failing to respond to standard therapies.