X-ray examination X-ray examination can understand the location and size of lung cancer, and may see localized emphysema, pulmonary atelectasis caused by bronchial obstruction, infiltrative lesions or inflammation of lungs in the neighboring parts of the lesion. Bronchoscopy can directly observe the lesions of bronchial lining and lumen. Tumor tissue can be taken for pathological examination, or bronchial secretion can be sucked for cytological examination, in order to clarify the diagnosis and determine the histological type. Cytologic examination Sputum cytologic examination is a simple and effective method for lung cancer screening and diagnosis. Most primary lung cancer patients can find shed cancer cells in sputum. The positive rate of sputum cytology for central lung cancer can reach 70%～90%, while the positive rate of sputum test for peripheral lung cancer is only about 50%. If the nature of the lesion cannot be clarified after various examinations and short-term diagnostic treatments, and the possibility of lung cancer cannot be excluded, thoracotomy should be performed. In this way, it can avoid delaying the condition of lung cancer and losing the opportunity of early treatment. 5. ECT examination ECT bone imaging can detect bone metastases at an early stage, and both X-ray film and bone imaging have positive findings; if the osteogenic reaction of the lesion is static and metabolism is inactive, then bone imaging will be negative, and X-ray film will be positive, and the two are complementary to each other, so that the diagnosis rate can be improved. It should be noted that the false-positive rate of ECT bone imaging for diagnosing bone metastasis of lung cancer can reach 20%-30%, therefore, those with positive ECT bone imaging need to do MRI scanning of the bone in the positive area. Mediastinoscopy Mediastinoscopy is mainly used for patients with mediastinal lymph node metastasis, who are not suitable for surgical treatment and cannot obtain pathological diagnosis by other methods. Mediastinoscopy should be performed under general anesthesia. A transverse incision is made in the upper concavity of the sternum, the soft tissues of the anterior neck are bluntly separated to reach the anterior tracheal space, the anterior tracheal passage is bluntly freed, and a scope is placed to slowly pass behind the anonymous artery to observe the enlarged lymph nodes in the paratracheal area, tracheobronchial angle and sublongitudinal process, and the lymph nodes are dissected with special biopsy forceps to obtain lymph node tissues and sent to the pathology for examination.