[Anal intraepithelial neoplasia]

Human papillomavirus (HPV) is responsible for anal condylomata, anal intraepithelial neoplasia (AIN) and anal squamous cell carcinoma. AIN is a premalignant condition that can progress to invasive carcinoma through different grades of severity of the disease called AIN I, AIN II and AIN III. This paper looks at the current definition, diagnostic methods and management of AIN. The incidence of AIN has increased significantly in the last decades. The groups at risk are mainly patients with infection with human immunodeficiency virus, immunossuppressed patients and patients affected by HPV related diseases (e.g., cervical cancer or anal condyloma). Accurate diagnosis of AIN lesions consists of accurate grading and disease extension. Low grade AIN (AIN I) or in extensive lesions, follow-up is advised to determine the possible evolution to anal squamous cell carcinoma. In cases of more severe and localized lesions (AIN II and AIN III), surgical resection should be considered if the predictive postoperative morbidity is low. Screening programs for AIN are not currently in place and there might be much effort to study the management of HPV in these patients.