Evaluation of the 3-years anal carcinoma (AC) incidence in patient with anal AIN3 lesions, and factors associated with this AC. A retrospective cohort study will be conducted (2000-2013) followed by a prospective cohort study (starting in 2013) with new diagnoses of anal AIN3 lesion. The main outcome is histology proven AC. The 3-years incidence rate of AC will be calculated. Factors associated with AC will be estimated using a multivariate Cox regression model.