Ectopic thymus is when the thymus gland grows in a non-normal position. The normal thymus is located behind the sternum and in front of the pericardium and large blood vessels. Growths in other parts of the body, such as the neck, the edge of the pericardium, and the edge of the lungs, caused by various factors, are ectopic thymus. It is mainly caused by congenital and acquired factors. 1. Congenital factors: It is a rare congenital disease with different symptoms, which may be caused by alcohol abuse during the mother’s pregnancy, developmental mutation of the embryo, cellular immunity defects or functional defects, and manifested as special appearance, hypocalcemic convulsions, and congenital heart disease. 2. Acquired factors: due to bacterial and viral infections, inflammation stimulates the thymus, ectopic thymus mainly forms cysts and thymoma, all of which can cause ectopic thymus, which is mainly manifested as coughing, chest pain as well as chest tightness and discomfort. Surgery is the main treatment. There are many causes of ectopic thymus, according to their own situation, under the guidance of the doctor to identify the cause of the disease, symptomatic treatment.