Colon cancer is more common after middle age and manifests as diarrhea, bloody and purulent stools, and intestinal obstruction. X-ray examination shows localized lesions caused by tumors, with filling defects in the main lesions; when the lesions are located in the rectum, masses can be palpated; colonoscopy can detect cancer; biopsy can find cancer cells. Sometimes, ulcerative colitis can be complicated by colon cancer, or colon cancer can sometimes be complicated by colitis.