Clinically, many lung cancer patients have no symptoms, and often lung cancer is detected when doing routine physical examination, and the early symptoms of lung cancer are similar to other lung diseases, which also delay the treatment of lung cancer. Among the high-risk group, if symptoms of lung cancer are suspected, they should seek medical attention as early as possible and follow medical advice for necessary examinations, such as chest X-ray, sputum to find cancer cells, fiberoptic bronchoscopy, chest CT, percutaneous lung puncture, etc. Sometimes it is not possible to investigate once, so repeated examinations are needed until it is clear. Which people have high risk factors for lung cancer and need to receive frequent physical examination and X-ray review? Modern science shows that patients with lung cancer are at high risk of developing lung cancer because of the following factors: 1. Smoking: According to a lot of survey data from various countries, the cause of lung cancer is closely related to paper smoking. The increase in the incidence of lung cancer has a parallel relationship with the increase in the sale of paper cigarettes. Paper cigarettes contain many carcinogenic substances such as benzo(a)pyrene. Inhalation of paper cigarette smoke or application of tar in experimental animals can induce respiratory and skin cancer. The incidence of lung cancer is 10 times higher in people with smoking habits than in nonsmokers, and the incidence is even higher in heavy smokers, 20 times higher than in nonsmokers. At the end of this century, the incidence of lung cancer among female patients in Western European countries has increased significantly with the increasing number of women smokers. Among the clinically diagnosed lung cancer cases, those who smoked more than 20 cigarettes per day for more than 30 years accounted for more than 80%. In the past 20-30 years, the smoking situation in China is very serious, and nearly 300 million people have the habit of smoking. Beijing, Tianjin, Shanghai and other major cities, the male adult smoking rate of nearly 50%, nearly 5% of women, the number of young people who smoke is also a lot. Long-term smoking can lead to bronchial mucosa epithelial cell proliferation, squamous epithelial growth, inducing squamous epithelial cancer or undifferentiated small cell carcinoma. Although non-smokers can also develop lung cancer, adenocarcinoma is more common. Some domestic studies have concluded that people with a smoking index (i.e., the number of cigarettes smoked per day multiplied by the number of years of smoking) of 400 or more, or people over the age of 45 who smoke more than 20 cigarettes per day, are considered to be at high risk for lung cancer. 2. Occupational factors: In the 1930s, the high incidence of lung cancer in the Schneeberg mines in Europe was reported in the literature. After years of research, it is now recognized that long-term exposure to radioactive substances such as uranium, radium and their derivatives, carcinogenic hydrocarbons, arsenic, chromium, nickel, copper, tin, iron, coal tar, asphalt, petroleum, asbestos, mustard gas and other substances can induce lung cancer, mainly squamous and undifferentiated small cell carcinoma. The risk of lung cancer is further increased for those who are exposed to the above carcinogenic substances and smoke in the occupational environment. 3. Air pollution: The incidence of lung cancer is high in industrially developed countries, higher in cities than in rural areas, and higher in factories and mines than in residential areas, mainly due to the pollution of the atmosphere by harmful substances such as benzopyrene carcinogenic hydrocarbons from the combustion of oil, coal and internal combustion engines and asphalt highway dust in industrial and transportation developed areas. The survey material shows that the incidence of lung cancer increases in areas with high concentration of benzo(a)pyrene in the atmosphere. Atmospheric pollution and paper cigarette smoking may promote each other and play a synergistic role in the incidence of lung cancer. 4. Ionizing radiation: Miners exposed to radon and its daughters in the radiation environment have an increased risk of lung cancer. 5. Chronic lung diseases such as tuberculosis, silicosis and pneumoconiosis can coexist with lung cancer. The incidence of cancer in these cases is higher than that of 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, and on this basis, some cases may develop into cancer. 6. Intrinsic factors such as family inheritance, lowered immune function, metabolic activity and endocrine dysfunction may also play a role in promoting the development of lung cancer.