There is no very precise definition of a family history of cancer. Generally speaking, a family history of cancer is defined as having a high number of members of a family with the same type of cancer or multiple members with different types of cancer. Typically, patients with a family history of cancer have three or more close relatives who have had one or more types of cancer, or someone in the family who has had two or more primary cancers at several different sites. Factors leading to the occurrence of cancer include not only genetic predisposition, but also related to dietary habits, living environment, mental factors and so on. The most important cause of cancer development is mutation of cancer-related genes. Family history of cancer has a genetic predisposition, which will increase the risk of cancer in relatives, but it is not a certainty that they will develop cancer. It is recommended that people with a family history of cancer should go to regular hospitals for regular medical checkups to prevent cancer in a targeted manner. Once uncomfortable symptoms appear, they should seek medical treatment in time.