True adenocarcinoma of the anal canal arises from the anal glands around the dentate line, which pass radially outwards into the sphincter muscles. This tumour appears to have a poorer prognosis than either low rectal adenocarcinoma or ASCC, with a median survival of 33 months (in contrast to 118 months for ASCC). Due to its location, it often drains to the inguinal lymph nodes, spreads submucosally and should be treated aggressively with a combination of chemotherapy and radical surgery. The impact of radiotherapy is uncertain.