Mediastinal Mass

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DESCRIPTION

  • Mediastinal masses are lesions that arise within the anatomic space between the lungs.
  • Consideration of the three compartments of the mediastinum helps organize the differential diagnosis.
    • The anterior mediastinum includes the thymus, lymph nodes, ascending aorta, and other blood vessels.
    • The middle mediastinum includes the heart, great vessels, trachea, main bronchi, lymph nodes, and phrenic and vagus nerves.
    • The posterior mediastinum includes the esophagus, vertebrae, spinal cord, nerves, descending aorta, thoracic duct, lymph nodes, and azygous and hemiazygos veins.

EPIDEMIOLOGY

  • Anterior mediastinum
    • About half of mediastinal masses arise from the anterior mediastinal compartment, and ~60% of those are malignant.
    • The most common benign lesions include prominent thymus, thymic cyst, and lipoma.
    • The most common malignant lesions include thymoma, lymphoma, T-lymphoblastic leukemia/lymphoma, and germ cell tumor.
    • About 85% of Hodgkin lymphomas show intrathoracic involvement at presentation, most commonly affecting the anterior superior mediastinal lymph nodes.
    • About 50% of non-Hodgkin lymphoma cases have mediastinal involvement.
    • Germ cell neoplasms arise from collections of primitive germ cells that arrest in the anterior mediastinum. The most common germ cell tumor is a teratoma.
  • Middle mediastinum
    • Masses arising in the middle mediastinum are most commonly related to congenital cysts or malformations.
    • The most common benign lesions include bronchogenic cysts, infections (i.e., tuberculosis, fungal disease), and vascular malformations.
    • The most common malignant lesions include metastatic lymphadenopathy and cardiac/pericardial masses.
  • Posterior mediastinum
    • Masses arising in the posterior mediastinum are usually of neurogenic origin.
    • The most common benign lesions include neurofibroma, ganglioneuroma, vascular malformations, and extramedullary hematopoiesis.
    • The most common malignant lesions include neuroblastoma, ganglioneuroblastoma, and neurofibrosarcoma.

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