Anal cancer is a disease in which malignant (cancer) cells form in the tissues of the anus. The skin around the outside of the anus is called the perianal area. Tumors in this area are skin tumors, not anal cancer.  Being infected with the human papillomavirus (HPV) can affect the risk of developing anal cancer. Possible signs of anal cancer include bleeding from the anus or rectum or a lump near the anus. The prognosis (chance of recovery) depends on the size of the tumor, where the tumor is in the anus and whether the cancer has spread to the lymph nodes.