The mediastinum is a part of the thoracic cavity, located in the middle of the chest, bounded anteriorly by the sternum, posteriorly by the spine, and flanked by the mediastinal pleura. It is connected to the neck upward and extends downward to the diaphragm. It contains many vital organs and structures such as the heart, great vessels, trachea, esophagus, etc. Mediastinal tumors are a group of tumors originating from the mediastinum, including thymoma, intrathoracic goiter, bronchial cyst, dermatoid cyst, teratoma, lymphosarcoma, malignant lymphoma, pericardial cyst, lipoma, neural progenitor tumors, and esophageal cyst, etc., and are mostly benign. The mediastinum is often divided into four regions clinically. The upper mediastinum is the upper mediastinum and the lower mediastinum is the lower mediastinum. 2. Anterior-posterior division: the lower mediastinum is divided into anterior middle and posterior mediastinum with the pericardium as the boundary, anterior mediastinum before the pericardium, posterior mediastinum after the pericardium, and middle mediastinum after the pericardium. The anterior superior mediastinum had trachea, esophagus, thymus, great vessels, thoracic duct, vagus nerve, left recurrent laryngeal nerve, phrenic nerve and sympathetic trunk; the middle mediastinum had the pericardium, heart, ascending aorta, pulmonary blood vessels, superior vena cava, main bronchus and phrenic nerve; and the posterior mediastinum had the descending aorta, singular vein, thoracic duct, esophagus and lymph nodes. Clinical manifestations Nearly 1/3 mediastinal tumors are clinically asymptomatic, mostly found during physical examination, and malignant mediastinal tumors often have symptoms. Respiratory symptoms: chest tightness and chest pain often occur behind the sternum or on the affected side of the chest, and the pain is severe when the malignant tumor invades the bones or nerves. Cough is often caused by trachea or lung tissue pressure, hemoptysis is rare. 2.Neurological symptoms: the tumor compresses or erodes the nerves to produce various symptoms, such as phrenic nerve invasion causing eructation and diaphragmatic movement paralysis; laryngeal reentrant nerve invasion leading to hoarseness; sympathetic nerve involvement resulting in Horner’s syndrome; intercostal nerve erosion resulting in chest pain or sensory abnormality; compression of the spinal nerves resulting in paralysis of the limbs. Infection symptoms: if the cyst breaks down or the tumor infection affects the bronchial tubes or lung tissues, the corresponding infection symptoms will appear. Compression symptoms: compression of superior vena cava causes superior vena cava syndrome; compression of trachea and esophagus causes breathlessness and dysphagia. 5.Special symptoms: teratoma rupture into bronchial tube, patients cough up sebum and hair. The rupture of bronchial cyst connects with bronchus, and the patient may have the symptom of bronchopleural fistula. A few patients with intrathoracic thyroid tumors have symptoms of hyperthyroidism. Patients with thymic tumors are sometimes accompanied by symptoms of myasthenia gravis. Causes and pathogenesis: The causes of most of the tumors are still unclear. Some of the tumors are caused by ectopic cells or tissues planted into the mediastinal cavity, which abnormally proliferate and become tumors. Auxiliary examination 1.X-ray chest radiograph: preliminary diagnosis can be made. 2.Thoracic enhancement CT. 3.Thoracic enhancement CT. 2, Chest enhanced CT. 3, Tissue biopsy: percutaneous puncture biopsy or surgical biopsy. 4.Others: endoscopy, PET, MRI, ultrasound, radioisotope examination. Diagnostic basis 1, dry cough, chest pain, shortness of breath or hoarseness, diaphragmatic paralysis, superior vena cava compression syndrome and other symptoms and signs. 2, chest radiograph or CT found mediastinal lesions. 3.Biopsy pathology to clarify the diagnosis. Differential diagnosis Differentiate the nature and source of the tumor. Surgery is the main treatment method. Primary mediastinal tumors, no matter benign or malignant, should be surgically resected as early as possible once discovered. Other treatments include chemotherapy, radiotherapy, traditional Chinese medicine and biotherapy.