Intrathoracic goiter needs to be differentiated from the following anatomical structures and diseases: 1. Differentiation from hemangioma Intrathoracic goiter should be differentiated from an aneurysm of an unnamed artery and a lobe of a singular vein if it protrudes upward to the right; and from an aortic aneurysm if it protrudes to the left mediastinum. (1) The aneurysm of an unnamed artery does not move upward when the patient swallows, and the pulsation is sometimes visible under fluoroscopy. The pulsation is synchronized with the aortic wave. In some cases, it may cause rib destruction, and should be identified by chorography if necessary. (2) Lung texture can still be seen in the lobe of the singular vein, and the inverted comma-shaped singular vein can be seen near the hilum, and there is no compression of the trachea. Tracheobronchography should be performed if necessary. (3) Aortic aneurysm often elevates the aortic arch and displaces it upward, while retrosternal goiter displaces the aortic arch downward and to the left. Aortic aneurysms are often accompanied by dilatation of other parts of the aorta and enlargement of the heart. If necessary, a registered wave or aortography is feasible. In addition, aortic aneurysms or aneurysms without a name are more common to be syphilitic, and should be considered as aneurysms in the first place if they are positive for Wahl-Korn’s reaction. 2. Differentiate with neurogenic tumor. Intrathoracic goiter located in the posterior superior mediastinum should be differentiated from neurogenic tumor. 3. Differentiate with thymoma, which is also located in the anterior mediastinum but in a lower position than intrathoracic goiter, and is often combined with myasthenia gravis, simple erythrocyte dysplasia, hypogammaglobulinemia and other concomitant tumor symptoms. Surgical resection is required for pathologic diagnosis when identification is difficult.