Stage III anal cancer is divided into stages IIIA, IIIB, and IIIC. In stage IIIA, the tumor is 5 centimeters or smaller and has spread to lymph nodes near the anus or groin. In stage IIIB, the tumor is any size and has spread to nearby organs, such as the vagina, urethra, or bladder. Cancer has not spread to lymph nodes. In stage IIIC, the tumor is any size and may have spread to nearby organs. Cancer has spread to lymph nodes near the anus or groin.