Diagnosis of lung cancer: 1.MRI, i.e. MRI, can clarify the external invasion of tumor. 2.Needle aspiration cytology examination. Under the guidance of CT or MRI, a special needle can be used to puncture the lung mass to obtain tissue for cytological examination to clarify the cytological type of tumor. 3.Sputum cytology and pleural fluid cytology examination. Microscopic cytological examination can be performed on the patient’s sputum to clarify the tumor diagnosis. 4.Fibrinoscopy: The biopsy of the seen tissues can be performed by the open branch microscope, and the cytological diagnosis can be made by puncture biopsy of the mass through the fibrinoscope and alveolar lavage. 5.Mediastinoscopy. Biopsy of mediastinal lymph nodes can be performed to clarify whether there is lymph node metastasis. 6.Thoracoscopy. Thoracoscopy can clarify whether there is pleural metastasis of lung cancer, and wedge resection can be performed on the lung mass to obtain cytological diagnosis. 7.Positron emission tomography (PETCT) photography of lung cancer. PETCT can be used to diagnose lung cancer by using the different metabolism of normal cells and lung cancer cells to fluoride deoxyglucose. It can both localize and qualify, and is mainly used to exclude intra-thoracic lymph nodes and distant metastases. However, it is more expensive. 8.Carcinoembryonic antigen. In patients with lung cancer, carcinoembryonic antigen is significantly increased.