The posterior sternum, which is the back of the sternum. The sternum is located in the middle of the human chest cavity, from the neck to the saber, including the sternal stalk and sternal body above and the saber below; the posterior sternum has the mediastinum, including the trachea, esophagus, and aortic arch. If there is pain and burning sensation behind the sternum, it may be bile reflux gastritis or esophagitis, and gastroscopy is needed for further examination. If there is obstruction or choking sensation in eating, it may be esophageal cancer or cardia cancer, and gastroscopy is also needed. If there is a retrosternal goiter, which means that the thyroid gland is not located in the neck but behind the sternum, thyroidectomy is required.