Imaging examination 1. Chest X-ray: Chest X-ray is an important means for early detection of lung cancer and also one of the methods for postoperative follow-up. 2.CT examination of chest: CT examination of chest can further verify the location and involvement of lesions, and can also roughly distinguish their benign and malignant nature, which is an important means to diagnose lung cancer at present. Low-dose spiral chest CT can effectively detect early lung cancer, while CT-guided transthoracic lung mass aspiration biopsy is an important technique to obtain cytological and histological diagnosis. 3.B-type ultrasonography: It is mainly used to detect important abdominal organs and whether there are metastases in the abdominal cavity and retroperitoneal lymph nodes, and also used to examine double supraclavicular fossa lymph nodes. 4.MRI examination: MRI examination has certain value for clinical staging of lung cancer, especially for determining whether there are metastases in the spine, ribs and skull. 5.Bone scan examination: it is a routine examination for determining bone metastasis of lung cancer. When bone scan examination suggests suspicious metastasis, MRI examination can be performed to verify the suspicious area. 6.PET-CT examination: It is not recommended for routine use. It has higher sensitivity and specificity than CT in diagnosing mediastinal lymph node metastasis of lung cancer. Endoscopic examination. 1.Fiber bronchoscopy: fiber bronchoscopy technique is the most commonly used method to diagnose lung cancer, including brush examination under direct vision of fiber bronchoscope, biopsy and bronchial lavage to obtain cytological and histological diagnosis. The combination of these methods can improve the detection rate. 2.Transfiber bronchoscopy-guided transmural puncture mediastinal lymph node biopsy (TBNA) and fiberoptic ultrasound bronchoscopy-guided transmural lymph node puncture biopsy (EBUS-TBNA): Transfiber bronchoscopy-guided transmural lymph node puncture biopsy is useful for accurate N2 staging of TNM stage of lung cancer before treatment. However, it is not routinely recommended as an examination method and should be actively carried out in hospitals with conditions. Trans-fiber ultrasound bronchoscopy-guided transmural lymph node aspiration biopsy (EBUS-TBNA) can provide more safe and reliable support for accurate pathological diagnosis of lung cancer N1 and N2. Mediastinoscopy: As an effective method to confirm the diagnosis of lung cancer and assess N stage, it is the gold standard for clinical evaluation of mediastinal lymph node status of lung cancer. Although CT, MRI and PET-CT, which has been applied in clinical practice in recent years, can provide valuable evidence for N-stage of lung cancer before treatment, they still cannot replace the diagnostic value of mediastinoscopy. 4.Thoracoscopy: Thoracoscopy can accurately diagnose and stage lung cancer. For early stage lung cancer that cannot be detected by fiberoptic bronchoscopy and transthoracic wall lung mass aspiration biopsy (TTNA), especially for small nodular lesions in the lung, thoracoscopic resection of the lesion can be a clear diagnosis. For middle and late stage lung cancer, biopsy of lymph nodes, pleura and pericardium, cytological examination of pleural fluid and pericardial effusion can be performed under thoracoscopy to provide a reliable basis for the formulation of comprehensive treatment plan. Other examination techniques 1.sputum cytology examination: sputum cytology examination is one of the simple and convenient non-invasive diagnostic methods to diagnose lung cancer. 2.Transthoracic wall intrapulmonary mass puncture needle aspiration biopsy (TTNA): TTNA can be performed under the guidance of CT or B-ultrasound, which is more sensitive and specific in diagnosing peripheral lung cancer. 3.Thoracocentesis: When the cause of pleural fluid is unclear, thoracocentesis can be performed to further obtain cytological diagnosis and to clarify the stage of lung cancer. 4.Pleural biopsy: When no positive cytology result is found by pleural puncture, pleural biopsy can improve the positive detection rate. 5.Superficial lymph node biopsy: For patients with occupying lung lesions or those who have been clearly diagnosed as lung cancer, if accompanied with superficial lymph node enlargement, superficial lymph node biopsy should be routinely performed to obtain pathological diagnosis, further determine the stage of lung cancer and guide clinical treatment. Blood immunobiochemical examination. 1.Blood biochemical examination: For primary lung cancer, there is no specific blood biochemical examination. For lung cancer patients, elevated plasma alkaline phosphatase or blood calcium may be considered as bone metastasis, and elevated plasma alkaline phosphatase, ghrelin, lactate dehydrogenase or bilirubin may be considered as liver metastasis. (2) Blood tumor marker examination: Currently, there are no specific lung cancer markers used for clinical diagnosis, so it is not a routine examination item. (1) carcinoembryonic antigen (CEA): Currently, CEA is mainly used to determine the prognosis of lung cancer and to monitor the treatment process. (2) Neuronespecific enolase (NSE): It is the preferred marker for small cell lung cancer and is used for diagnosis and monitoring of treatment response in small cell lung cancer. (3) cytokeratinfragment (CYFRA21-1): It has some reference significance for the sensitivity and specificity of lung squamous carcinoma diagnosis. (4) Squamous cell carcinoma antigen (SCC): it is valuable for monitoring the efficacy and prognosis of lung squamous cell carcinoma. Histological diagnosis Histopathological diagnosis is the basis of lung cancer diagnosis and treatment. When the diagnosis of lung cancer is confirmed by biopsy, standardized treatment should be performed. If the pathology of biopsy cannot confirm the pathological diagnosis due to the limitation of biopsy sampling, it is recommended that clinicians repeat biopsy or combine with imaging examination to further choose the treatment plan, and if necessary, joint consultation between clinicians and pathologists should be conducted to confirm the pathological diagnosis.