(See also Overview of Pleural and Mediastinal Disorders.)
The mediastinum (chest cavity) refers to an area that is bordered by the breastbone (sternum) in front, the spinal column in back, the neck on top, and the diaphragm below. It contains the heart, the thymus gland, some lymph nodes, and parts of the windpipe (trachea), esophagus, aorta, thyroid gland, and parathyroid glands. It does not include the lungs.
Doctors classify masses according to which part of the mediastinum they develop in: the front (anterior), middle, or back (posterior—see figure Locating the Mediastinum). The area in which the mass develops may provide a clue to the cause.
Mediastinal masses may be
Noncancerous masses include cysts in the heart and pouch-like sacs or bulges that develop in the wall of an organ, such as the esophagus (called a diverticulum) or the aorta (called an aneurysm). Organs may enlarge, as occurs when a goiter forms in the thyroid gland or when cancer (such as a lymphoma) or an infection causes the lymph nodes to enlarge. Children may have birth defects in the mediastinum (for example, cysts, blood vessel abnormalities, or abnormal development of the esophagus).
Masses in the mediastinum occasionally cause no symptoms, especially small masses in adults. Masses, including cancers, are more likely to cause symptoms in children.
The most common symptoms in adults and children are chest pain and weight loss. Some masses cause fever. Others cause difficulty swallowing. In children, mediastinal masses are more likely to cause cough or shortness of breath due to airway compression.
Masses in the mediastinum are often discovered when a chest x-ray is taken or another imaging test is done to evaluate symptoms such as chest pain, cough, or difficulty breathing or is done for another reason. Additional tests, usually computed tomography (CT) or magnetic resonance imaging (MRI) and biopsy, are needed to determine the cause of the mass.
Treatment depends on the cause. If the mass is not cancer and is causing no symptoms, doctors may monitor the person regularly instead of treating the mass. Cancers may be removed surgically or treated with chemotherapy. An infection that causes swollen lymph nodes is usually treated with antibiotics or antifungal drugs.