Key disease processes in the mediastinum include mediastinitis and mediastinal masses. Pneumomediastinum is an additional mediastinal abnormality that can result from alveolar rupture, esophageal perforation, or dissection of air from the neck or abdomen. Diagnosed by chest radiography, pneumomediastinum typically does not require specific treatment.

Mediastinitis can be an acute or chronic process. Acute mediastinitis can result from esophageal perforation, following cardiac surgery with median sternotomy, or from infections in the neck, oral cavity, or face. Esophageal perforation can occur spontaneously or iatrogenically; surgical exploration of the mediastinum, repair of the esophageal perforation, and drainage of the pleural space and mediastinum are required. Mediastinitis after median sternotomy typically presents with wound drainage and is diagnosed by mediastinal needle aspiration. Treatment requires immediate drainage, debridement, and IV antibiotics.

Chronic mediastinitis can range from granulomatous lymph node inflammation to fibrosing mediastinitis. Most cases are due to tuberculosis or histoplasmosis.

Different types of mediastinal masses are found in the anterior, middle, and posterior mediastinal compartments. The most common mass lesions in the anterior mediastinum are thymomas, lymphomas, teratomas, and thyroid lesions. In the middle mediastinum, vascular masses, enlarged lymph nodes (e.g., metastatic cancer or granulomatous disease), and bronchogenic or pleuropericardial cysts are found. Posterior mediastinal masses include neurogenic tumors, gastroenteric cysts, and esophageal diverticula.

Chest CT scans are invaluable for evaluating mediastinal masses. Biopsy procedures are typically required to diagnose mediastinal masses; needle biopsy procedures (e.g., percutaneous or bronchoscopy), mediastinoscopy, and thoracoscopy are potential options.