The anus is the canal that connects the lower part of the large intestine (the rectum) to the outside of the body. Anal cancer is fairly rare. Different cancers can develop in different parts of the anus, part of which is inside the body and part of which is outside. Sometimes abnormal changes of the anus are harmless in their early stages but may later develop into cancer. Some anal warts, for example, contain precancerous areas and can develop into cancer. The main type of anal cancer is squamous cell carcinoma of the anus.
