Imaging (X-ray, CT) findings of lung mass or occupancy do not necessarily mean lung cancer, but a pathological diagnosis (also called cytological diagnosis) is required to confirm the diagnosis of lung cancer 100%. There are 9 methods to obtain pathological diagnosis as follows: 1. Fiberoptic bronchoscopy: fiberoptic bronchoscopy is the most common method to diagnose lung cancer, including brush examination under direct vision, biopsy and bronchial lavage to obtain cytological and histological diagnosis. 2. Transfiber bronchoscopy-guided transmural aspiration mediastinal lymph node biopsy (TBNA) and fiberoptic ultrasound bronchoscopy-guided transmural lymph node aspiration biopsy (EBUS-TBNA): Transfiber bronchoscopy-guided transmural lymph node aspiration biopsy is useful for accurate N2 staging of pre-treatment lung cancer TNM staging. However, it is not routinely recommended, and should be actively performed in hospitals that are able to do so. Transfiber 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 the N stage, it is currently the gold standard for clinical evaluation of the status of mediastinal lymph nodes in lung cancer. Although CT, MRI and PET-CT, which has been applied to clinical practice in recent years, can provide valuable evidence for N-staging before lung cancer 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 clearly diagnose the disease. 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. 5. Sputum cytology examination: sputum cytology examination is one of the simple and convenient non-invasive diagnostic methods to diagnose lung cancer, and sputum cytology smear examination can be obtained by taking sputum after deep cough in the morning for three consecutive days. 6. Transthoracic thoracic aspiration biopsy (TTNA): TTNA can be performed under the guidance of CT or B-ultrasound, and has higher sensitivity and specificity in diagnosing peripheral lung cancer. 7. Thoracentesis: When the cause of pleural fluid is unclear, thoracentesis can be performed to obtain further cytological diagnosis and to clarify the stage of lung cancer. 8. Pleural biopsy: When no positive cytological result is found by pleural puncture, pleural biopsy can improve the positive detection rate. 9. Superficial lymph node biopsy: For patients with occupying lung lesions or clearly diagnosed lung cancer, if there is 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.