Anterior mediastinal mass

Anterior mediastinal masses can be caused by neoplastic and non-neoplastic pathology. These masses arise in the anterior mediastinum, that portion of the mediastinum anterior to the pericardium and below the level of the clavicles. 

Epidemiology

The prevalence of anterior mediastinal masses on CT is estimated at 0.4-0.9% ⁴.

Differential diagnosis

The differential diagnosis for an anterior mediastinal mass includes ^1-3:

• thymus

  • thymoma: most common primary neoplasm of the anterosuperior mediastinum

  • invasive thymoma

  • thymic carcinoma

  • thymolipoma/thymoliposarcoma

  • thymic cyst

  • thymic hyperplasia

  • thymic carcinoid

• thyroid and parathyroid masses

  • thyroid neoplasms

  • thyroid goiter

  • parathyroid neoplasms

• lymphoma

  • Hodgkin lymphoma 

  • non-Hodgkin lymphoma

• germ cell tumors

  • mediastinal teratoma

    • mature: 75% of mediastinal germ cell tumors

    • immature

    • teratocarcinoma (malignant teratoma)

  • mediastinal seminoma

  • mediastinal embryonal carcinoma

  • mediastinal yolk sac tumor

  • mediastinal choriocarcinoma

  • mediastinal mixed cell type germ cell tumor

• vascular masses

  • thoracic aortic aneurysm

  • subclavian artery aneurysm

A handy mnemonic to remember the major categories is the 5 Ts.