In most cases, these mutations are caused by diet or aging, but in about 10% to 20% of colorectal cancer patients, the mutations are passed from parents to offspring, i.e., they are inherited. It is found that the risk of colon cancer is many times higher for those who have one or more first-degree relatives with colon cancer than for the general population, and the younger the age of the affected relatives, the higher the risk of colon cancer. How to determine hereditary colorectal cancer? When more than two generations of members in a family develop colorectal cancer, it should be suspected whether the family is a family with hereditary colorectal cancer. Members of hereditary colorectal cancer families usually develop colorectal cancer or colorectal adenoma at a younger age, and some members may also develop benign or malignant tumors in other areas. Therefore, members of the family concerned need to undergo regular medical checkups for early detection and treatment. In most cases, colorectal cancer specialists are able to determine whether it is hereditary colorectal cancer by investigating and analyzing the incidence in the family of a certain colorectal cancer patient. However, in some new cases, in addition to detailed understanding of the patient’s condition, colorectal cancer specialists sometimes need to rely on molecular biology to determine whether the patient carries a heritable gene mutation. Common hereditary colorectal cancers There are many types of hereditary colorectal cancers, some of which are easier to diagnose, such as hereditary non-adenomatous colorectal cancer (HNPCC) and familial adenomatosis (FAP), which are the most common in clinical practice, while others have atypical clinical features or are recessive in nature, making them more difficult to diagnose. ”Hereditary non-adenomatous colorectal cancer” is the most common autosomal dominant syndrome among colorectal cancers, accounting for 2% to 6% of colorectal cancers. Patients have an early age of onset and are prone to multiple colorectal cancers, and in addition to colorectal cancer, their family members are also prone to endometrial cancer, gastric cancer, genitourinary tumors and small bowel cancer. Another common hereditary colorectal cancer – “familial adenomatosis” is also an autosomal dominant syndrome, accounting for 1% of colorectal cancers, with adenomatous polyps and microadenomas spreading throughout the colon and numbering more than 100. About 60% to 70% of patients with familial adenomatosis have a clear family history of colorectal cancer or polyps, while another 30% of patients have no family history of new cases. Why are some patients with no family history of colorectal cancer also hereditary colorectal cancer? During fertilization, parents pass only one set of their chromosomes to their offspring, so when one parent has one set of normal chromosomes and one set of mutated genes, the probability of the offspring getting the mutated genes is 50%, and once the chromosome carrying the mutated genes is passed to the offspring, the offspring will inherit a certain disease, such as hereditary colorectal cancer. In this case, although the parents are normal, the chromosomes of the germ cells that develop into the offspring contain mutated genes, so the offspring are still prone to certain diseases, and such mutations can be passed on to the next generation of the offspring, which means they are hereditary. Scientific prevention and control of hereditary colorectal cancer Hereditary colorectal cancer usually goes through the process from adenoma to cancer, so receiving fiberoptic colonoscopy and removing colorectal polyps during follow-up is an effective means of prevention. Most scholars believe that those whose first-degree relatives have colorectal cancer or adenoma should undergo regular colonoscopy from the age of 40; if the relatives have early age of onset, regular examination should be started from 3 to 10 years before that relative’s age of onset. Over the past decades, scientists have gradually gained an in-depth understanding of the pathogenesis of hereditary colorectal cancer by accumulating cases and applying advanced molecular biology methods, and hereditary non-adenomatous colorectal cancer, familial adenomatosis, and some other key genes related to hereditary colorectal cancer have been discovered one after another, making it possible to diagnose hereditary colorectal cancer through genetic testing. Not only does genetic testing help avoid missing suspected cases, but when the mutated locus of a pre-documented person (the first patient in the family to be diagnosed with hereditary colorectal cancer by a doctor) is identified, genetic testing can be performed on members of his or her family to screen out high-risk members who carry the mutated gene; while family members who do not carry the mutated gene (i.e., do not inherit the mutated gene) are spared the hassle of regular checkups and the psychological