The presence of a mass on the surface of the sigmoid colon with erosion and necrosis may be caused by colon cancer. Colon cancer is a malignant neoplastic disease with abnormal proliferation of mucosa on the surface of sigmoid colon, and the typical symptoms are abdominal pain, blood in stool, and weight loss. Its colonoscopy mainly shows the presence of cauliflower pattern swelling on the surface of colon, and necrotic erosion and bleeding on the tissue surface of the swelling. However, the diagnosis should be confirmed by biopsy of the pathological tissues taken out under colonoscopy. Colon cancer is mainly treated by surgical resection. If the tumor can be completely removed, radical resection is preferred. If the tumor cannot be completely removed, palliative surgery can be performed to alleviate the symptoms, which can also be combined with chemotherapy, targeted therapy and other treatment modalities to improve the treatment effect to a certain extent. If there is a swelling on the surface of the sigmoid colon with erosion and necrosis, the patient should seek medical treatment in time, and should not take any action without authorization, so as to avoid delaying the condition. Pay attention to rest on weekdays, quit smoking and drinking, and rationalize the diet.