It is now believed that the heredity of tumors exists. Although 80%-99% of human tumors are caused by environmental factors, there are still some tumors related to genetic factors. Generally speaking, the relationship between human tumors and genetic factors has the following forms:

(1) Genetic factors play a decisive role in tumorigenesis, that is, so-called hereditary tumors, such as retinoblastoma, nephroblastoma, neuroblastoma, colonic polyposis with multiple adenomas, etc. These are rare familial tumors, all inherited by a single gene.

(2) Genetic factors do not determine the occurrence of tumors, but only the susceptibility of tumors, that is, individuals with this characteristic are prone to some tumors in general. For example, xeroderma pigmentosum patients are prone to skin cancer or melanoma under sunlight. Due to the lack of endonuclease, these patients can't repair the DNA damage caused by ultraviolet rays, which leads to cell canceration.

(3) Genetic factors and environmental factors play a synergistic role in tumorigenesis. At present, it is found that some common tumors also have family history, such as breast cancer, gastric cancer, intestinal cancer, liver cancer, nasopharyngeal cancer and so on. These tumors are influenced by genetic factors, but environmental factors may play a more important role.