The chest (thoracic) cavity is a space that is enclosed by the spine, ribs and sternum (breast bone) and is separated from the abdomen below by the diaphragm. The chest cavity contains the heart, the thoracic aorta, lungs, and esophagus (swallowing passage) among other important organs.
The wall of the chest cavity is made up of the rib cage and diaphragm. The chest wall is firm enough to protect the organs in the chest cavity but flexible enough to move outward and inward with respiration (breathing). As is the case with any other structure in your body, the chest wall can develop tumors.