Anatomy

As the widest part of the interpleural space, the middle mediastinum contains the heart, the ascending aorta, the superior vena cava, the bifurcation of the trachea into two bronchi, pulmonary artery and veins, phrenic nerve, and lymph nodes. An irregular triangular space running parallel with the vertebral column, the posterior mediastinum, contains esophagus, thoracic duct, lymph nodes, descending aorta, veins, spinal nerves and ganglions, sympathetic trunk, and associated ganglia and paraganglia. The boundary for the posterior mediastinum anteriorly is the pericardium, posteriorly is the paravertebral sulci from the lower border of the T4 to T12, laterally is the mediastinal pleura, inferiorly is the diaphragm, and superiorly is the transverse thoracic plane (Fig. 12.1).

Clinical features

Diverse mass lesions can occur in middle and posterior mediastinum. The majority of these lesions present as an asymptomatic mass on chest X-ray. When symptoms occur, they are usually related to impingement on local structures, resulting in chest pain, dyspnea, dysphagia, cough, superior vena cava syndrome, or neurologic deficits. Middle mediastinum is the primary site for pericardial cysts, bronchogenic cysts, and lymphomas. Posterior mediastinum is the site for neurogenic tumors. Soft tissue tumors and metastatic tumors occur in both middle and posterior mediastinum. Children tend to get lymphomas, neuroblastoma, ganglioneuroblastoma, and sarcomas, whereas in adults, the most common tumors are carcinomas from the lung and esophagus followed by neurogenic tumors and lastly cysts and soft tissue tumors.