Adenomatous polyps are pathologically known as neoplastic polyps, and it is clinically proven that adenomatous polyps in the large intestine can develop into colorectal cancer over several years, i.e., it takes about 10 years for adenomatous polyps in the intestine to develop into cancer. Familial adenomatous polyps appear in large numbers at the age of 10-20 years, and most of them are adenomas, and most of them become cancerous just after the age of 30 years, therefore, preventive resection should be done at the age of 20-25 years at the latest.