I. Mediastinal zoning and its corresponding characteristics with common tumors Felson’s three-zone method is simple and practical, that is, it is divided into anterior, middle and posterior regions by longitudinal alignment on the lateral chest radiograph. There are other methods, such as four-zone method and nine-zone method. The diagnosis is based on the location of the mass in the subdivision: intra-thoracic goiter or tumor, tumor of thymus, germ cell tumor (teratoma) and pericardial cyst are common in the anterior mediastinum. Tumors and tumor-like lesions in the middle mediastinum include lymphatic tumors and non-neoplastic lymph node enlargement, and tracheal and bronchial cysts are often located in the middle mediastinum. In the posterior mediastinum, neurogenic tumors and esophageal tumors are most common, and non-neoplastic descending aortic aneurysms and paravertebral abscesses are also more common. The significance of CT and MRI in determining whether mediastinal tumors can be resected by VATS (1) Mediastinal tissues and organs: CT and MRI show the mediastinal tissues and organs clearly and realistically, close to anatomical observation, and are morphological studies in vivo, which are clear and intuitive in determining the relationship between mediastinal masses and mediastinal tissues and organs, and are crucial in the qualitative diagnosis of mediastinal masses. For example, the close relationship between the thyroid gland and the trachea often leads to deformation and displacement of the trachea by compression. The lymphatic tissues in the mediastinum are most abundant in the paratracheal and bronchial areas, and nodules or masses in this area are most commonly enlarged lymph nodes (tumorigenic and non-tumorigenic). The posterior mediastinum is rich in nerve tissue, and neurogenic tumors are most common in this area. The esophagus and descending aorta are also located in the posterior mediastinum, as well as infections of the spinal bones can also form posterior mediastinal masses, which must be considered in the differential diagnosis. (2) Mediastinal hiatus: Between the mediastinal tissues and organs, there are certain constant hiatuses, and in adults, these hiatuses are rich in adipose tissue, small blood vessels and lymphatic tissue, which can be clearly shown by advanced CT and MRI. III. Relationship between common mediastinal hiatuses and VATS resection ① posterior sternal or prevascular hiatus, which corresponds to the anterior mediastinal region of the X-ray division, contains normal thymus or degenerated thymic tissue, adipose tissue and lymphatic tissue, etc.; ② main pulmonary artery window, trachea and peribronchial hiatus, including the anterior-posterior tracheal hiatus and the subruminal hiatus, contains rich lymphatic tissue and corresponds to part of the middle mediastinal region of the X-ray division; ③ The posterior mediastinal space, including the peri-esophageal space and the peri-descending aortic space, and the posterior spinal sulcus area next to the spine; ④ The odd vein esophageal fossa is formed after the right lung extends to the right main bronchus and heart to reach the right edge of the esophagus and odd vein. Esophageal tumor and lymph node enlargement can cause deformation of this fossa. This is a gap-obscured area for X-ray examination, which cannot be shown by ordinary chest X-ray. The logical thinking procedure of VATS resection analysis and judgment of mediastinal masses ①Whether it is a mediastinal lesion: differentiate mediastinal masses from mediastinal lung cancer; ②Localization diagnosis: clarify the position of the mass in the mediastinal X-ray partition; ③Qualitative diagnosis: preliminary analysis and diagnosis of benign and malignant nature and tissue origin of the mass; ④Observation and analysis of the mass and its relationship with mediastinal tissues and organs: observe the mass itself and its contact with mediastinal organs through CT or MRI examination. (4) Observation and analysis of the mass and its relationship with the mediastinal tissues and organs: through CT or MRI examinations, the morphological performance of the mass itself and its contact surface with the mediastinal organs and the morphological performance of the fat layer are observed, and the possibility of benign and malignant mediastinal masses is inferred. ⑤ Comprehensive analysis and treatment plan: comprehensive imaging performance, closely combined with clinical and laboratory test results, make preliminary diagnosis and formulate treatment plan. V. Indications for VATS mediastinal tumor surgery Mediastinal organs without obvious invasion; cystic lesions of any size; solid lesions depending on the specific situation, preferably less than 5 cm. Common cystic lesions Mediastinal cysts Anterior intestinal cysts Pericardial cysts Thymic cysts VI. Contraindications for VATS mediastinal tumor surgery Extensive adhesions and invasion with surrounding important organs without normal borders; malignant tumors: giant thymoma, thymic carcinoma, germ cell tumors The main nerves are: phrenic nerve, sympathetic trunk and stellate ganglion, vagus nerve, laryngeal anticranial nerve, spinal nerve; pay attention to the relationship between the direction of the left and right phrenic nerves and the position of the tumor; the protection method of phrenic nerve.