MEDIASTINAL DISEASE



The mediastinum is bounded by the thoracic outlet, the diaphragm, the sternum, the vertebral column, and the medial borders of the lungs. It contains the heart, esophagus, trachea, lymphat­ics, thymus gland, and a large number of nerves and blood vessels. Generally, benign mediastinal masses grow slowly, displace surrounding struc­tures, and are painless, whereas malignant lesions invade and compress the important mediastinal structures, giving rise to earlier symptoms such as pain, dysphagia, hoarseness, stridor, cough, and dyspnea and features of Horner’s and superior vena cava syndromes. Myasthenia gravis is as­sociated with thymomas, while neurogenic tu­mors cause spinal cord or nerve compression.

The chest x-ray localizes the process and often suggests the correct diagnosis. CT is invaluable, as it separates vascular from nonvascular lesions and cystic from solid structures and identifies local invasion. Definitive diagnosis often depends on obtaining tissue.