Stage III anal cancer is divided into stages IIIA and IIIB. In stage IIIB, the tumor may be any size and has spread to (1) nearby organs and to lymph nodes near the rectum; or (2) lymph nodes on one side of the pelvis and/or groin, and may have spread to nearby organs; or (3) lymph nodes near the rectum and in the groin, and/or to lymph nodes on both sides of the pelvis and/or groin, and may have spread to nearby organs.