The mediastinum is located between the lungs on both sides, with the sternum and thoracic vertebrae as its front and back boundaries. There are many important organs in it, including large blood vessels, trachea, main bronchi, pericardium, esophagus, thymus, and a large amount of fat, nerves, lymphatic vessels and other tissues. Due to abnormal congenital development or acquired cysts or tumor formation, it becomes a mediastinal tumor. There are many types of tumors in the mediastinum, some are primary and some are metastatic. Benign primary tumors are more common, but a considerable number of them are malignant. In order to indicate the location of the lesion in the mediastinum, the mediastinum can be divided into several parts, divided into upper and lower parts at the level of the sternum and the lower edge of the fourth thoracic vertebra. The mediastinal space containing many important organs is called the "visceral organ mediastinum" (middle mediastinum), the space in front of the right trachea and pericardium is the anterior mediastinum; the space behind the trachea and pericardium (including the esophagus and paraspinal mediastinum) is called the posterior mediastinum. According to domestic statistics, neurogenic tumors rank first in the incidence of mediastinal tumors, followed by teratogenic tumors, thymic tumors and thyroid tumors, and various cystic tumors are the least common.