TNM staging of colon cancer is the most commonly used method in clinic, and clear staging is needed before surgery and radiotherapy or chemotherapy for colon cancer. First of all, we need to know that T stands for the condition of primary lesion; N stands for the condition of lymph nodes; M stands for the presence of metastasis to distant organs. TNM staging of colon cancer: 1. T stands for primary tumor: Tx: unable to estimate the primary tumor; T0: no evidence of tumor; Tis: carcinoma in situ; T1: tumor invades the submucosal layer or mucosal muscular layer; T2: intrinsic muscular layer involvement; T3: invades to the subplasma membrane; T4: penetrates the plasma membrane layer. 2.N stands for regional lymph nodes: Nx: no estimation of lymph nodes; N0: no lymph node metastasis; N1: 1 to 3 regional lymph nodes metastasis; N2: 4 and more than 4 regional lymph nodes metastasis. 3. M stands for distant metastasis: Mx: unable to estimate distant metastasis; M0: no distant metastasis; M1: distant metastasis.