After conservative treatment anal mucosal biopsies enable exclusion of neoplastic cells only on the endoluminal surface. We used transanal full thickness tru-cut needle biopsies in the follow-up of 11 anal tumors. Full thickness tru-cut needle biopsies showed malignant cells in the fibrous tissue in 3 patients and few cells with atypical nuclear features in another 2. All diagnostic exams resulted negative. Therefore, needle biopsies were helpful to diagnose neoplastic remainder. Multiple samples are necessary to reduce the false negative number. This method is simple, relatively inexpensive, easily repeatable and not burdened with complications.