I. Exogenous carcinogenic factors 1. Physical carcinogenic factors: heat, chronic mechanical stimulation, ultraviolet light and other long-term chronic stimulation. For example, the bad habit of eating too hot and hard food for a long time in esophageal cancer. Chronic mechanical stimulation – Tongue cancer often occurs in the place where caries, broken teeth, or unsuitable dentures rub for a long time; gallbladder stones are often combined with gallbladder cancer; scalp cancer often occurs in Islamic disciples who often stimulate the scalp by shaving with blunt knives; cervical laceration caused by multiple births leads to cervical cancer; scrotal contusion can lead to testicular tumor; many patients with bone sarcoma and breast cancer also have a history of trauma. Long-term exposure to X-rays or ultraviolet radiation. Chemical carcinogenic factors: chromium can cause lung cancer; nickel can cause lung cancer and nasopharyngeal cancer; long-term exposure to arsenic can cause skin cancer and liver cancer; cadmium can cause prostate cancer; other factors such as lead, iron, zinc, sulfur and molybdenum can also cause tumors. Air and water pollution such as coal combustion, automobile exhaust – are cyclic hydrocarbons (3-4 benzopyrene) such as lung cancer urban than rural, such as chimney sweep workers are prone to scrotal cancer, exposure to coal tar is prone to skin cancer; smoking and passive smoking – benzopyrene, toluene, dimethylnitrosamine, thiocyanate cause lung cancer, oral cancer, esophageal cancer, pancreatic cancer, bladder cancer, etc. Nitrosamines can induce esophageal cancer, stomach cancer, lung cancer, liver cancer and colon cancer. 3.Biological carcinogenic factors: viruses – herpes-like virus (EBV) is related to nasopharyngeal cancer, breast cancer, leukemia, cervical cancer, malignant melanoma, infectious mononucleosis, multiple B-cell lymphoma, Burkitt’s lymphoma and certain sarcomas; herpes simplex virus is related to cervical cancer; human papillomavirus (HPV) is related to tongue, throat and cervical cancer; C-type RNA virus is related to leukemia; B RNA virus is related to breast cancer; hepatitis B virus is related to liver cancer; human immunodeficiency virus (HIV) is related to Kapozi’s sarcoma; molds – some food, food additives, vegetables contain molds such as Aspergillus, Fusarium, Streptomyces and Aspergillus, etc. Among them, the aflatoxin produced by Aspergillus has a strong carcinogenic Parasites: Schistosoma haematobium is related to the development of intrahepatic bile duct cancer, and Schistosoma japonicum is related to rectal cancer and colon cancer. Certain drugs can also cause cancer. Endogenous cancer-causing factors 1. endocrine dysfunction: sex hormone disorder is related to breast cancer and uterine tumor, and male sex hormone disorder is related to prostate cancer; 2. neuropsychiatric factors: long-term mental overstress is prone to tumor. Genetic factors: retinoblastoma, nephroblastoma, pheochromocytoma, neuroblastoma, colon adenocarcinoma, breast cancer, stomach cancer, etc. have genetic tendency or family aggregation 4. immune status: the immune system of the body has the function of identifying abnormal mutated cells or tumor cells and destroying or destroying them to prevent the occurrence of tumor, which is the immune surveillance function. T lymphocytes in the body can recognize tumor cells and transform into sensitized lymphocytes that can attack and kill tumor cells after receiving stimulation from tumor cells, which has immunosurveillance function. The thymus is an important organ in the immune system, and experiments have proved that the thymus and the cellular immunity related to it play a major role in inhibiting tumor growth. A part of lymphocytes can be differentiated into immunologically active T cells only by the action of thymic humoral factors. Animals with thymus removal and those with congenital hypoplasia of the thymus show cellular immune defects and an increased incidence of tumors. In addition to sensitized T cells, K cells, NK cells and macrophages also have immune surveillance functions to kill tumor cells. Plasma cells, which are differentiated from B cells, produce specific antibodies that are destructive to various tumor cells and play an important role in anti-tumor humoral immunity as well. For example, tumor antigens stimulate the body and produce complement-dependent cytotoxic antibodies, which can effectively destroy tumor cells when the antibodies bind to them in the presence of complement; also, anti-tumor IgG-type antibodies can help K cells to kill tumor cells. When immunosuppression or immunodeficiency occurs, it can often cause lymphoreticular system and virus-related tumors. Secondary immunodeficiency can be seen in medical-derived immunodeficiency, such as organ transplant recipients with long-term application of immunosuppression are prone to tumors, and immunosuppression caused by extensive radiation and chemotherapy may produce another tumor while the original tumor is effectively treated. This may be due to the long-term or heavy use of immunosuppressive drugs that impair the immune surveillance function of the lymphoreticular system and reduce the body’s surveillance of tumor cells or mutated cells. Modern medicine believes that there are about 10 trillion cells in the human body, and tens of thousands of cells may become malignant every day due to various external and internal factors, but they are constantly destroyed or suppressed by the strong defense immune system of the human body, and generally do not develop. If the immune system is damaged due to various reasons such as malnutrition, physical weakness, long-term over fatigue or mental stress and trauma, as a result, the body “fails to monitor” the tumor cells, and the tumor cells take the opportunity to grow in large numbers, and their speed exceeds the speed of immune system to identify and remove the tumor cells, then the tumor will occur. It is due to the influence of internal and external factors, after a long process, the cells of tissues and organs cause progressive and severe atypical proliferation, and eventually become cancer. This period is called the induction period and is generally 15-30 years long.