Definition

Stage III colorectal cancer is divided into stages IIIA, IIIB, and IIIC. In stage IIIA, (1) cancer has spread through the mucosa (innermost layer) of the colon and/or rectum wall to the submucosa (layer of tissue next to the mucosa) or to the muscle layer of the colon and/or rectum wall. Cancer has spread to one to three nearby lymph nodes or cancer cells have formed in tissue near the lymph nodes; or (2) cancer has spread through the mucosa of the colon and/or rectum wall to the submucosa. Cancer has spread to four to six nearby lymph nodes.