The occurrence of lung cancer is the result of the interaction of multiple factors. In recent years, the incidence of lung cancer has continued to rise, and among male cancer patients, lung cancer has taken the first place. The etiology of lung cancer is still not completely clear, but a lot of information shows that long-term heavy smoking is an important causative factor of lung cancer. The incidence of squamous and undifferentiated lung cancer is 4-10 times higher than that of nonsmokers for those who smoke more than 40 cigarettes per day for many years, and the incidence of lung cancer in urban residents is higher than that in rural areas, which may be related to atmospheric pollution and carcinogenic substances in cigarette smoke. Therefore one should quit smoking and strengthen urban environmental sanitation. Lung cancer, as a respiratory disease, is a familiar disease. Most of the symptoms of lung cancer are: wheezing, cough, chest and back pain, hemoptysis and so on. Lung cancer is divided into central type lung cancer and peripheral type lung cancer. Peripheral type may have changes of chest pain once the tumor accumulates to the pleura at the time of detection, and if it develops further, it will have pleural lesions and will produce pleural effusion. Central type lung cancer generally has slightly earlier lung cancer symptoms because it occurs in the main bronchial tubes, and cough, sputum and blood or chest discomfort appear earlier. Clinical manifestations of lung cancer in different periods 1.Early stage of lung cancer: clinical manifestations are heavier than latent, but the symptoms are still mainly persistent cough or choking cough, blood in sputum, hemoptysis, severe chest pain or no pain instead, long-term low fever, and people are more emaciated. 2.Middle and late stage of lung cancer: severe choking cough, shortness of breath, blood in sputum, hemoptysis, severe or no pain in chest pain, long-term low fever, more obvious weight loss, or pleural effusion, swelling of face and limbs, unfavorable urination, etc.