Thymoma is a relatively rare tumor originating from thymic epithelial cells or thymic lymphocytes, usually located in the anterior superior mediastinum. Thymoma grows slowly, and even after the disease has progressed, some patients still have a long survival time, with a 5-year survival rate of nearly 90%. 1. Causes: At present, it is believed that the development of thymoma may be related to genetic factors and infectious factors. 2. Symptoms: patients with thymoma may not have any clinical symptoms, and the most typical symptoms are tumor compression symptoms, such as Horner’s syndrome, hoarseness, numbness and pain in the upper arm, dyspnea, cough, fever, coughing up sputum, jugular vein varicose, swelling of the upper limbs of the face and difficulty in swallowing, and so on. 3. Treatment: Thymoma is usually treated by surgery, complete resection of the tumor, i.e. thymus tissue, including mediastinal adipose tissue, even if the tumor has invaded the surrounding tissues, there are still chances of surgery, but postoperative radiotherapy and chemotherapy should be assisted as follow-up treatment. Because of the biological characteristics of thymoma such as recurrence after resection and invasion and metastasis in a small number of thymoma tumors, all thymic tumors have been regarded as malignant tumors at present, and should be treated by surgery as soon as they are detected.