Not all cancers are genetically determined, but the occurrence of cancer is closely related to the activation of oncogenes and the inactivation of oncogenes. Cancer occurs mainly as a result of the interaction of multiple cancer-causing factors, including internal factors and external environmental factors. Cancer may be caused by internal factors, such as genetic factors, immunologic factors, endocrine factors, etc. Everyone has different genes, and some people are born with genetic defects that are likely to be passed on to the next generation. People with congenital immunodeficiency are prone to malignant tumors and are also prone to cancer when there are abnormal hormone levels in the body. Cancer may be caused by external factors such as chemical carcinogens, physical carcinogens and biological carcinogens. Industrial gases contain high levels of carcinogens that damage the DNA of healthy cells and increase the risk of cancer. In addition, radiation and drug abuse can cause genetic mutations. Genetic testing not only screens for susceptibility genes, but also identifies genetic mutations in the body. When there is cancer, it is important to actively pursue treatment to increase the cure rate of cancer.