Recently, a patient asked this question: “My family member is suffering from bowel cancer, and it is said that bowel cancer is hereditary, and no one in his previous generation had this disease, now my son is 20 years old, do I need to pay attention to it? Does my son need to eat with separate dishes? Will there be any contagion in this process?” Here is the answer to the question “Is colon cancer hereditary? Is colon cancer contagious?” Can colon cancer be hereditary? –Colorectal cancer is hereditary 1. Colorectal cancer is hereditary to a certain extent. Studies show that if a colorectal cancer patient is found in a certain family, the probability of colorectal cancer in relatives related to him (parents, children, siblings, Fig. 8-1) is significantly higher, and the incidence of colorectal cancer is about 2-3 times higher than that in the general population. The risk of colorectal cancer is even higher if two or more close relatives (parents or siblings) in the family have colorectal cancer. This is especially true for a young colorectal cancer patient, which is more closely associated with genetic factors, and who has a higher incidence of colorectal cancer in his immediate family. However, there is no need to be alarmed by this. These figures only remind us that relatives of bowel cancer patients should have colonoscopy as early as possible so that colorectal cancer can be detected and treated as early as possible. Figure: Family tree. Relatives who are related to the patient by blood. 2. The heritability of colorectal cancer is not particularly strong. Colorectal cancer is not like some hereditary diseases, if the parents develop the disease, the children will definitely develop the disease. Because the occurrence of colorectal cancer is the result of both environmental factors and genetic factors, even if the genetic background of two people is exactly the same, if they are exposed to different environments, the probability of their occurrence of colorectal cancer is not the same. Therefore, children of colorectal cancer patients are not 100% likely to get colorectal cancer. However, please note that although the majority of colorectal cancers are sporadic, about 10% to 15% of colorectal cancers have a hereditary background, with familial adenomatous polyposis (FAP) accounting for about 1% to 2%, hereditary nonpolyposis colorectal cancer (HNPCC) accounting for 2% to 7%, and other cases such as pemphigus fugax polyposis (PJS) and juvenile polyposis. Here, we will introduce two diseases in detail: familial adenomatous polyposis and hereditary non-polyposis colorectal cancer. Family Adenomatous Polyposis (FAP) The common feature of this disease is the widespread distribution of a large number of adenomatous polyps of varying sizes on the mucosa of the large intestine, which are arranged in dense clusters or strings, and their number can often be as many as hundreds or even thousands. The polyps range from the size of a soybean to several centimeters in diameter and are often densely arranged. Patients are born without colorectal polyps. Most of the polyps appear around the age of 15, and the number of polyps is small at the beginning, but increases with age, and there are hundreds or thousands of polyps in the whole colon during the patient’s teenage years. The larger the polyp, the more likely it is to become cancerous. 100% of FAP cases will become cancerous if left untreated, and most FAP polyps become cancerous in their 30s, with the average untreated death occurring at around 42 years of age. FAP is an autosomal dominant disease, which means that once a patient develops the disease, his or her children will have a 50% chance of developing it. Therefore, family members of FAP patients need to be screened by colonoscopy, and once FAP is detected, it should be surgically removed as soon as possible to prevent cancer from developing over time. Therefore, if one of the parents has FAP, their children should have regular colonoscopy from about 10-12 years old until they are 50 years old. The patient’s parents and siblings should also have colonoscopies because they are also at risk for developing FAP. Patients with familial adenomatous polyposis have densely packed polyps of varying sizes in the colon. Hereditary non-polyposis colorectal cancer (HNPCC) is diagnosed as follows: (1) At least three people in the family have been diagnosed with pathologically confirmed hereditary non-polyposis colorectal cancer-related cancers (colorectal, endometrial, gastric, ovarian, small intestinal, ureteral, and pelvic, bile duct, brain, and skin cancers) and one of them is a direct descendant of the other two people. (2) must involve 2 consecutive generations; (3) at least 1 person with colorectal cancer onset earlier than 50 years of age; (4) exclude familial adenomatous polyposis. This disease is characterized by early age of onset, high incidence of multiple primary colorectal cancers, and high incidence of intra- and extra-colorectal malignancies in family members. There are 60%-80% of patients will have colorectal cancer before 60 years old, which accounts for 5%-10% of the total incidence of colorectal cancer. Is colorectal cancer contagious? –Colorectal cancer is not contagious. Colorectal cancer is not contagious. Infectious diseases are often caused by a pathogen (such as bacteria or virus), and bacteria or virus can be transmitted from one person to another when they are spread through certain media (such as saliva, blood, mosquito). Colorectal cancer is caused by a combination of genetic and environmental factors, not by a certain pathogen, so it is impossible to transmit colorectal cancer to others. Speaking of which, some people may ask, “Since colon cancer is not contagious, why is it that one person in a family has colon cancer, and after some time, other family members are found to have colon cancer again?” This is because people in the same family have a similar genetic background. If one person develops bowel cancer, it means that the genetic background of this family is prone to bowel cancer, so the probability of other family members developing bowel cancer is also higher. On the other hand, as members of the same family share common dietary habits because they live together for a long time, if they are high in protein, high in fat, low in fiber, prefer barbecue food, etc., they are also prone to bowel cancer because they share the same risk factors. Therefore, colorectal cancer shows certain family aggregation.