Patients often ask: Is cancer contagious and do cancer patients need to be isolated? Cancer itself is not contagious. There are 3 conditions for contagiousness: infectious source, transmission route and susceptible people. Cancer cells do not release infectious factors, so they are not contagious. However, some patients say: I and my family members have tumors, so is it contagious? It is worth mentioning that in recent years, the family aggregation exhibited by cancer has been paid more and more attention. The high incidence of stomach cancer, or breast cancer, or lung cancer in the same family is increasingly making people talk about cancer. What is family aggregation all about? Take gastric cancer as an example, 10% of gastric cancers manifest as familial aggregation of gastric cancers, which may be caused by strong genetic susceptibility genes or similar dietary and living habits of family members. For example, some families like to eat pickled food or salty food, some families like to eat spicy food, some families like to drink alcohol, etc., all of which are likely to trigger gastric cancer. In addition, H. pylori infection is another important factor that triggers stomach cancer. The rate of H. pylori in our population is 61%, which is quite high, mainly because our population is characterized by sharing utensils in their eating habits, coupled with unclean and uncontrolled diet, which is very easy to cause mutual infection in a family. Coupled with the unfavorable factors such as the same living environment and habits, it is also possible to induce family gathering of stomach cancer. In addition to stomach cancer, the family aggregation of lung cancer is also becoming more and more obvious. If a family is exposed to long-term decoration pollution or second-hand smoke, the chance of getting lung cancer in the family will increase. Women whose mothers or sisters in the family have had breast cancer have a 3 times higher incidence of breast cancer than the average woman. However, you cannot attribute all the causes of breast cancer to heredity. Breast cancer occurs as a result of many factors, including celibacy, not breastfeeding, and being easily moved. Finally, cancer cells are not contagious, but one thing that does become contagious is a virus. The main cancers we know of that are caused by viruses are: nasopharyngeal cancer caused by EBV, cervical cancer caused by human papillomavirus (HPV), and liver cancer associated with hepatitis B and C viruses. Among patients with primary liver cancer, the positive rate of hepatitis B virus infection is 86.22% or higher, and the risk of liver cancer in hepatitis B virus-infected patients is 13.52 times higher than that in non-infected patients. The transmission of hepatitis B virus is through mother-to-child, blood and sexual transmission, which also shows some indication of family aggregation. What I want to explain above is that cancer is not contagious, but its family aggregation manifestation cannot be ignored. All we can do is to have regular medical checkups, strengthen our own exercise, enhance our immunity, eat healthy, work and rest healthily, and keep our body and mind happy. Even if there are cancer cells left in the net, we can use our own immunity to destroy them.