Rectal cancer infiltrating fat of 3cm means that at this time the tumor has invaded to the intrinsic muscular layer and is accompanied by distant metastasis of 2 lymph nodes, according to the TMN staging system of rectal cancer, the patient is at stage III of rectal cancer at this time. According to TMN staging system, the patient is now in stage III rectal cancer. The rectal irritation symptoms of stage III rectal cancer are more obvious, with pus and blood stools after the cancer breaks down and may be accompanied by lower abdominal pain. If the cancer invades and causes narrowing of intestinal tube, there will be incomplete intestinal obstruction such as abdominal pain, abdominal distension and hyperactive bowel sounds. Due to lymph node metastasis, the cancer may invade surrounding tissues or metastasize to distant organs (e.g. prostate, bladder, vagina, etc.), causing corresponding symptoms. The stage of rectal cancer can roughly assess the prognosis of patients, and the five-year survival rate of patients with stage III rectal cancer is about 70%. Treatment mainly consists of surgical resection of tumor and adjuvant radiotherapy, which can effectively improve the prognosis of rectal cancer patients. If the clinical staging result of rectal cancer patients is 3cm of invasive fat with 2 lymph nodes metastasis, they should be treated under the guidance of doctors, establish confidence in treatment and actively cooperate with treatment to prolong their life.