What is colon cancer? Colon cancer shows malignant growth in the colon. Adenomatous polyps of the colon are considered precancerous lesions of colon cancer. What are the symptoms caused by colon cancer? Black mucus stools, irregular bowel movements and changes in stool texture may occur. Rectal cancer can also present with an urgency and heaviness. High-grade tumors may also present with abdominal pain. Occult blood tests may be positive. Who are the high-risk patients? Colon cancer is one of the most common cancers. Tumors can be stopped by removing colon polyps. Polyps can be easily removed during colonoscopy. However, there is not much awareness of prevention and colonoscopy is not well utilized as part of preventive medicine screening. Therefore, it is important to perform colonoscopy on those who are at high risk for colon cancer. High-risk groups: 1. Among blood relatives who have colon cancer or colon polyps; 2. People with a history of colon cancer or who have had colon polyps removed; 3. Diabetes mellitus; 4. Overweight people; 5. Women with breast, uterine, and ovarian cancers; 6. Smokers; and 7. Patients with long-term inflammatory bowel disease.