What are the causes and symptoms of lung cancer?

       Lung cancer usually occurs in the bronchial mucous touch epithelium. It is also called bronchial lung cancer. Lung cancer accounts for 90-95% of all substantial lung tumors. According to the World Health Organization, lung cancer is currently the number one cause of cancer deaths worldwide, accounting for approximately 19% of all malignancies.  Known factors that can increase the risk of the disease are mainly the following: 1. smoking.  2.Atmospheric pollution.  3. Occupational factors.  4. Chronic lung diseases, etc.  The most common symptoms of lung cancer are: 1. cough, mostly irritating cough, no sputum or a small amount of white sticky sputum. 2.  2. Hemoptysis, mostly bloody sputum or blood in sputum; 3. Chest tightness and chest pain  4.Fever, mostly persistent and low fever in lung cancer, which is repeatedly delayed.  5.Difficulty in breathing, shortness of breath, etc.