Intrathoracic goiter is a simple enlargement of the thyroid gland or thyroid tumor in the posterior sternum or mediastinum. It is not easily detected because it is located behind the sternum or in the mediastinum, making diagnosis and treatment difficult. Intrathoracic goiter, like cervical goiter, is a multinodular non-toxic benign thyroid tumor. Sometimes the benignity of the tumor and the malignancy between the tumor and nodular hyperplasia are not easily diagnosed before surgery. Intrathoracic goiter accounts for 9% to 15% of thyroid disease, and this proportion has been increasing in recent years, with more women than men. Clinical manifestations are caused by compression of the surrounding organs by the mass. If compression of the trachea causes dyspnea and wheezing; compression of the superior vena cava causes superior vena cava syndrome such as angry superficial veins in the upper chest and neck and edema in the upper limbs; compression of the esophagus causes difficulty in swallowing. The esophagus is softer than the trachea and can still escape the pressure of the tumor even if the esophagus is compressed or displaced. The severity of symptoms is related to the size and location of the mass. Patients often have different degrees of hunchback, thick and short neck, obesity, and some patients have a history of thyroid surgery.