There are no obvious symptoms in the early stage of colorectal cancer. Because the cancer cells are from the colon mucosa and the colon intestinal lumen is thicker, generally the tumor is relatively small in the early stage and will not block the intestinal lumen without obstruction performance, that is, there is no abdominal distension/abdominal pain and it does not affect the exhaustion and defecation, so there can be no feeling. In addition, the tumor does not have ulcer or the stool does not cause the tumor to rupture, and it will not cause bleeding problem. Even if there is a small amount of bleeding, as long as the coagulation function is normal, the bleeding stops quickly and there will not be fleshly black stools or fresh blood stools. It may be positive for fecal occult blood. Therefore, there will not be obvious symptoms either. Therefore, it is said that early stage of bowel cancer is basically undetectable. Unless the patient has a family history of tumor or has the habit of regular physical examination colonoscopy, it can be detected early. Colon cancer is a common and frequent cancer However, as the tumor grows and enters the middle or late stage, the corresponding symptoms will gradually appear and become obvious. For example, difficulty in defecation, especially if the tumor is located in the left half of the colon, descending colon/sigmoid colon/rectum, because the stool is formed and the lumen of the left half of the colon is thin, the symptoms of difficulty in defecation will appear relatively early. In addition, the bowel lumen of ascending colon is thick and has enough space for the tumor to grow, in addition, the stool is not shaped, so it is not easy to have intestinal obstruction. When the tumor enters advanced stage, besides the symptoms caused by the primary focus as mentioned above, there are also symptoms caused by the metastatic focus. Cough, dyspnea, breath-holding (caused by lung metastasis, pleural effusion); pain in right upper abdomen, reduced appetite, even jaundice (caused by liver metastasis); chronic pain in multiple places all over the body (bone metastasis possible); abdominal bulging, bloating (peritoneal metastasis possible); bilateral ovarian swelling (ovarian metastasis); neck mass (supraclavicular lymph node metastasis).