Overview 1. Malignant tumor, i.e. cancer, is a new organism formed when normal cells in human body become cancerous under the action of various carcinogenic factors, so that normal cells become malignant cancer cells and local tissues proliferate abnormally. Those originating from epithelial tissues are called cancer, such as lung cancer and cervical cancer; those originating from mesenchymal tissues are called sarcoma, such as fibrosarcoma, liposarcoma and osteosarcoma. 2.At present, it has become one of the most serious diseases threatening human health. According to the statistics of 16 common cancers all over the world, 6.35 million cases occur every year, among which China estimates 1 million, and 800,000 people die from cancer every year, that is, an average of 2,000 people are taken out of life by cancer every day. 3. Malignant tumors cause a lot of labor loss and high medical cost, such as the United States in 1990 alone, cancer treatment cost 104 billion dollars, which causes a lot of consumption of social data, and also brings immeasurable mental loss to patients and families. The prevalence characteristics of malignant tumors 1) From the perspective of regional distribution There are differences between different countries and regions, and the distribution of the same malignant tumor varies in different regions. For example, liver cancer is common in Europe and America, and is highly prevalent in Japan, Malaysia, Indonesia, Singapore and coastal areas and provinces south of Yangtze River in China. Especially, Qidong in Jiangsu and Fusui in Guangdong. Gastric cancer has a high incidence in Japan, Chile, Finland, Austria, Iceland and China’s Gansu Hexi Corridor, Jiaodong Peninsula, and coastal Jiangsu and Zhejiang. Esophageal cancer is common in northeastern Iran, South Africa (spot homogeneous), Kenya, etc. Henan, Shanxi, Hebei and Beijing in China are the high incidence areas (especially Lin County in Henan), centered on Taihang Mountains and gradually decreasing in all directions. The incidence of intestinal cancer in China is also on the rise year by year, and is higher in the south of Yangtze River than in northern China. Nasopharyngeal cancer is highly prevalent in Southeast Asia and South China (Guangdong, Guangxi, Yunnan, Jiangxi, Hubei), and the incidence rate of nasopharyngeal cancer among overseas Chinese is higher than that of local people. (2) In terms of urban and rural distribution, lung cancer is the leading cause of death of malignant tumors in China, and stomach cancer is the leading cause of death in rural areas. The mortality rate of colon, rectal and anal cancer in urban population is significantly higher than that in rural area, while the mortality rate of cervical cancer in rural area is significantly higher than that in urban area. (3) From the population distribution characteristics, tumor incidence differs among different age, gender, race, occupation, migration and other populations. Malignant tumors can occur at any age, but the incidence rate mostly increases in parallel with age. Leukemia, brain tumor and malignant lymphoma are most common in children; liver cancer and leukemia are common in young adults; stomach, esophagus, cervical and lung cancer are most common in middle and old age. The gender distribution of malignant tumors is more frequent in men than in women, about 1.99:1, and the only tumors higher in women than in men are gallbladder, thyroid, breast and reproductive tract; occupational bladder cancer mainly occurs in rubber and cable manufacturing industries, and occupational lung cancer is more frequent in industries exposed to asbestos, arsenic, chromium, nickel and radioactive mining. The racial differences of malignant tumors are very obvious, nasopharyngeal cancer is mostly seen in Chinese Cantonese; primary liver cancer is mostly seen in African spot homoeopaths, oral cancer is more frequent in Indian population, esophageal cancer is more common in Kazakhs, and cervical cancer is rare in Israeli Jews. The main risk factors of malignant tumors 1) Behavior and lifestyle Smoking is related to the development of many cancers, among which the closest relationship is with lung cancer. Cigarette smoking can increase the mortality rate of lung cancer by more than 10 times, and the earlier the age of smoking and the greater the amount of smoking, the greater the risk of lung cancer. In addition to lung cancer, smoking can also cause cancers of the mouth, pharynx, larynx, esophagus, pancreas, bladder and other cancers. Alcohol consumption is related to oral cancer, pharyngeal cancer, laryngeal cancer and rectal cancer. Long-term alcohol consumption can lead to cirrhosis of the liver and then may be associated with liver cancer. Drinking alcohol and smoking can increase the risk of certain malignant tumors. Pickled foods, salted vegetables, etc. are risk factors for stomach cancer; sodium nitrite is a preservative, which forms nitrosamines with amines in an acidic (PH3.0) environment, the latter being a carcinogenic substance. Aspergillus flavus contaminated rice, wheat, corn, peanuts, soybeans, etc. to produce aflatoxin, carcinogenic; smoked, baked foods such as smoked sausage, ham, etc. can contain carcinogenic substances benzo(a)pyrene. The risk of esophageal and gastric cancer increases when the food is refined, long-term iron deficiency and nutritional deficiency. Low selenium concentration in the diet and low blood selenium level are prone to malignant tumors. 2) Environmental physical and chemical factors According to the World Health Organization, 80%-90% of human malignant tumors are related to environmental factors, the most important of which are environmental chemical factors. About 10% of lung cancer cases are caused by air pollution (including the combined effect with smoking). Ionizing radiation can cause a variety of human cancers, such as acute and chronic granulocytic leukemia, multiple myeloma, malignant lymphoma, lung cancer, thyroid cancer, breast cancer, stomach cancer, liver cancer, etc. 3) Psychosocial factors Unique emotional life history can lead to the occurrence of cancer. Unfortunate family events, excessive work-study stress, uncoordinated interpersonal relationships, early death or divorce of parents in childhood, further setbacks in adulthood, widowhood, career failure, grief and continuous stress leading to despair, etc. are all important psychosocial factors that lead to cancer. The personality characteristics of individuals are also related to malignant tumors: (1) sentimental and depressed; (2) irritability, poor patience, silence and cold attitude towards things; (3) isolation and eccentricity; long-term loneliness, contradiction, disappointment and depression are important factors that promote the growth of malignant tumors. Some people call this kind of personality as “cancer personality”. (4) Drug Factors At present, there are many kinds of drugs that can induce malignant tumors. For example, long-term use of estrogen can cause vaginal and cervical cancer, arsenic can cause skin cancer, excessive exposure or acceptance of radionuclides, iodine and phosphorus can cause acute leukemia, long-term use of finasteride can induce renal pelvis disease, chloramphenicol can cause aplastic anemia, which is also a pre-leukemia lesion, and cyclophosphamide can treat cancer, but it can also induce leukemia, breast cancer and bladder cancer. (5) Occupational factors Occupation-related risk factors include physical factors such as ionizing radiation, ultraviolet light, and exposure to various chemical carcinogens. (6) Viral factors Currently, hepatitis B virus (primary liver cancer), EB virus (lymphoma, nasopharyngeal cancer) and herpes simplex virus type II (cervical cancer) are considered to have a close relationship with human tumors. Pathogenesis 1. It is generally believed that the pathogenesis of malignant tumors is the result of the combination of genetic and environmental factors, but according to a recent study by researchers of the National Cancer Institute, special attention should be paid to the following three aspects, which deserve further in-depth study: 1) the emergence of abnormal genes is the basis of cell carcinogenesis; 2) various oncogenic factors are the triggers to initiate abnormal gene mutations; 3) abnormal genes become oncogenes and immune function; 4) the development of cancer is the result of the mutation of the immune system. (3) the transformation of abnormal genes into oncogenes is related to immune dysfunction. Therefore, the early examination of abnormal genes is more clinically important than the morphological examination of cancer cells. 2. Human understanding of tumor pathogenesis has gone through a long process, from single and physical carcinogen, chemical carcinogen, viral carcinogen and mutation carcinogen theory to multi-step and multi-factor comprehensive carcinogen theory in the past. (a) Chemical carcinogen: At present, any chemical substances that can cause tumor formation in humans or animals are called chemical carcinogens. According to their mode of action, they are divided into three categories: direct carcinogens, indirect carcinogens and carcinogenic substances.