Lynch syndrome refers to people with mismatch repair gene mutations that predispose them to colorectal cancer and other malignancies, including those who already have tumors that have not yet occurred. It is the most common hereditary colorectal cancer syndrome, accounting for 2%-5% of the colorectum, and was named hereditary non-adenomatous colorectal cancer, in order to emphasize its hereditary nature and differentiate it from familial adenomatous disease, as well as to emphasize the relevance of Lynch syndrome to colorectal cancer. The main diagnostic criteria include the following: 1. at least three or more cases of Lynch syndrome-related cancer in the family, including colorectal cancer, endometrial cancer, small bowel cancer, ureteral and renal pelvis cancer, one of which is a direct relative of the other two cases; 2. at least two consecutive generations of involvement; 3. at least one person younger than 50 years old at the time of diagnosis; 4. except familial adenomatosis; 5. tumor confirmed by pathology as colorectal The tumor is pathologically confirmed as colorectal cancer. Lynch syndrome is a hereditary disease, which is an autosomal dominant disease with a high heredity rate. Therefore, if a patient with colorectal cancer has been diagnosed with Lynch syndrome, it is recommended that his or her children undergo genetic counseling, and if the offspring also have mismatch repair gene defects, regular colonoscopy can be performed for early prevention and early treatment to achieve a cure.