Generally, the tumor stage is not based on the size of rectal tumor, but mainly based on the depth of tumor invasion to the intestinal wall and the number of lymph node metastasis around the rectum and the root of the mesenteric vessels, which means that the overall stage is determined by combining the results of T stage and N stage. If there is no lymph node metastasis in T1 or T2 stage, it is generally stage I rectal cancer; if there is no lymph node metastasis in T3 or T4 stage, it is generally stage II rectal cancer; if there is lymph node metastasis, regardless of T1 or T2 stage, it is stage III rectal cancer; if there is distant metastasis, including peritoneal implantation metastasis, liver metastasis or lung metastasis, etc., it is called stage IV rectal cancer.