Mediastinal tumors are a group of tumors originating in the mediastinum, including thymoma, intrathoracic goiter, bronchial cyst, dermatoid cyst, teratoma, lymphosarcoma, malignant lymphoma, pericardial cyst, lipoma, neurogenic tumors, and esophageal cyst, with benign ones being the most common. Teratomas are mostly seen below the age of 30 years, and the rest of them occur more often above the age of 40 years. The prognosis of this disease is good except for lymphosarcoma and malignant lymphoma. Commonly used examination I. Imaging examination 1. Chest X-ray: It is an important means to diagnose mediastinal tumor. It is also the main diagnostic method. Chest X-ray can show the location, shape, size, density and calcification of mediastinal tumor, and under X-ray fluoroscopy, it can also observe whether there is any throbbing of the block shadow, whether it moves up and down with swallowing, whether it can change its shape with position or breathing movement, etc. According to the above characteristics, most of the mediastinal tumors can be diagnosed by X-ray examination, and most of them have a good prognosis. According to the above characteristics, most mediastinal tumors can be initially diagnosed. CT scan: CT scan has almost become a routine, which can provide many information that chest X-ray cannot provide. Secondly, CT scan has its superiority in the identification of fatty, vascular, cystic and soft tissue masses. In addition, CT scan can show the relationship between the neighboring structures and tissues invaded by the tumor. 3.Magnetic resonance imaging (MRI): MRI is superior to CT in determining whether neurogenic tumors have intradural or intradural extension; MRI does not need contrast agent to distinguish tumors from macrovascular diseases; MRI can provide sagittal and coronal images in addition to cross-sectional images. 4.Ultrasonography: Although ultrasonography has great value in the differential diagnosis of substantial, vascular or cystic tumors. However, it has not been widely used clinically due to the specificity of the mediastinal mass site. In most cases, it has been replaced by CT, MRI or nuclear scanning. 5.Isotope scanning: It can assist in the diagnosis of retrosternal goiter. 6, PET-CT PET is the abbreviation of Positron Emission computed Tomography, which is translated into Chinese as: Positron Emission Computerized Tomography, also known as PET. At present, the commonly used clinical imaging agent is 18F-FDG, mainly reflecting the body’s glucose metabolism, can be early detection of malignant tumors, Alzheimer’s disease. Invasive examination 1, fine needle biopsy under fluoroscopy, CT or ultrasound guidance; 2, fiberoptic bronchoscopy, fiberoptic gastroscopy (help to clarify the bronchial and esophageal pressure, whether the tumor invades the bronchial tube or esophagus, so as to determine the possibility of surgical resection); 3, thoracoscopy (VATS) (for biopsy to confirm the diagnosis, to understand the tumor location, character and adjacency, and to carry out partial Mediastinoscopy (can clarify whether there are enlarged lymph nodes in the paratracheal and subglottic region, and tissue biopsy is feasible); 5. Cervical lymph node biopsy; 6. Cesarean section (if the nature of the tumor is not clarified by various examinations, and the systemic condition permits, cesarean section may be performed to explore the nature of the tumor); 3. Tumor markers (abnormally high levels of AFP, HCG, CEA, and LDH in the blood should be considered for the possibility of malignant germ cell tumor. (Abnormal elevation of serum AFP, HCG, CEA and LDH should be considered as malignant germ cell tumor. Neurogen-specific enolase (NSE), norepinephrine and epinephrine levels are helpful in the diagnosis of neurogenic tumors) Treatment Principles Mediastinal tumors, except for malignant tumors such as lymphosarcoma, which are suitable for radiotherapy and chemotherapy, should be treated surgically in the vast majority of cases. Asymptomatic benign mediastinal tumors and cysts should also be surgically removed if there is no contraindication for surgery. There are also some mediastinal tumors, such as thymoma, which are difficult to determine their benign or malignant nature before surgery, and if they are not treated with timely surgery, the timing of surgery may be delayed.