Small cell lung cancer is a kind of lung cancer, so its manifestation and treatment methods are different. The main causes of small cell lung cancer: 1. Smoking The relative risk of dying from lung cancer among smokers is 12.7, and those who smoke more than 30 cigarettes a day have a 22.3-fold increase in relative risk compared to non-smokers. 82% of lung cancer deaths or 31600 deaths in the United States in 1985 could be attributed to smoking. Many epidemiological studies have been done at home and abroad on the relationship between smokers and different tissue types of lung cancer, and most of the findings concluded that smoking is closely related to squamous lung cancer and small cell lung cancer. At the same time, studies have shown that the risk of dying from lung cancer can be reduced to the level of nonsmokers after 10-15 years of quitting smoking. 2. Environmental tobacco smoke is composed of sidestream smoke released from burning tobacco and smoke exhaled by smokers, which account for 80% and 20%, respectively. ETS contains a variety of toxic substances, including mutagens and carcinogens, such as some chemicals (nitrite, 4-aminobiphenyl, benzo(a)pyrene), which are higher in ETS than in the mainstream smoke released by burning tobacco. Studies have shown that passive smokers have levels of 4-aminobiphenyl-hemoglobin compounds that are approximately 14% of those of active smokers. Each year, 2%-3% of lung cancers diagnosed in smokers and non-smokers are caused by ETS. 3.Air pollution It is the pollution formed by the pollutant emission after sufficient dilution by air. With the development of industry, especially the emission of exhaust gas and gas from cities and factories, the mass production and use of various carcinogenic industrial raw materials and products, the carcinogenic substances in the air are increasing; the mass use of various means of transportation, especially the exhaust from automobiles, as well as asphalt in paving and construction, causes air pollution. In most countries, although lung cancer is mainly attributed to smoking, the risk of long-term exposure to urban air pollution in men with existing smoking habits is as high as 10 cases of lung cancer per 100,000 people per year. Thus, this outcome is the result of the interaction of tobacco with chemical compounds in the atmosphere and varies with geographic area and time. 4. Chronic lung diseases such as tuberculosis, silicosis, and pneumoconiosis can coexist with lung cancer. The incidence of these lung cancers is higher than normal people. In addition, chronic inflammation of lung bronchus and lung fiber scar lesions may cause squamous epithelial chemosis or hyperplasia during the healing process, on the basis of which some lung cancer patients may develop into carcinomas.