Lung cancer is currently the cancer with the highest incidence and prevalence rate, so it must be given sufficient attention, and early detection, early diagnosis and early treatment are of critical importance to the survival prognosis of patients. The following points can be used as reference to consider whether there are precursors of lung cancer: 1. long-term irritating cough for more than 2-3 weeks, which is ineffective after anti-inflammatory treatment; 2. sudden change in the nature of cough, such as the appearance of metallic or high-pitched cough; 3. recurrent blood in sputum or hemoptysis with no special cause; 4. recurrent lung infection, pneumonia or lung abscess in the same area, which has been treated with anti-inflammatory 5. The presence of focal segmental emphysema and pulmonary atelectasis requires high attention; 6. The presence of isolated round shadows on imaging or enlargement of one lung hilar; 7. The presence of joint pain and pestle finger without obvious cause; 8. The sudden change in the nature and shape of tuberculosis lesions in patients with pulmonary tuberculosis; 9. suspicion of tumorigenic lesions of the lung.