Staging for colon cancer is based on the TNM (tumor, node, metastasis) system. As demonstrated in this illustration, T1 tumors involve only the submucosa, while T2 tumors penetrate the submucosa and enter the underlying muscle tissue. T3 tumors penetrate through the colon's wall muscle, while T4 tumors penetrate through the bowel wall into the peritoneum. The T component of CRC staging is important because of its prognostic significance.

The N component of the staging system refers to regional lymph nodes. N0 indicates that no nodes are involved, while N1a indicates spread to a single node, N1b indicates spread to 2 to 3 nodes, N2a indicates that 4 to 6 nodes are positive, and N2b indicates that there are 7 or more positive nodes. Within each T stage, survival is inversely correlated with the N stage.

The M component of the staging system refers to metastasis, with M0 indicating the absence of any metastases. M1a is used to indicate metastasis limited to a single site, while M1b refers to metastasis to multiple distant sites.