Thymus
Thymus is behind the upper part of the sternum
The thymus gland lies in the chest, directly behind the breastbone (sternum), and in front of the heart in the area between the lungs called the anterior mediastinum.
Sometimes, however, the thymus gland is found in another (ectopic) location, such as in the neck, the thyroid gland, or on the surface of the lungs (the pleura) near the area where the blood vessels and bronchi enter the lungs.