Ectopic Anterior Mediastinal Pathology in the Chest: Radiologic-pathologic Correlation of Unexpected Encounters with the “Terrible Ts”

The complex embryology of the anterior mediastinum makes it home to an array of primary neoplasms tied to the presence of the thyroid and thymus glands in that compartment. While the occurrence of ectopic thyroid deposits in the extramediastinal thorax has not been convincingly established, the other three “Ts” of the classic “4T” mnemonic for the differential diagnosis of an anterior mediastinal mass have occurred in the lung parenchyma, pleural space, and endobronchially as primary tumors. Finding any of the three lesions – thymoma, teratoma, or B-cell lymphoma – in the chest outside the mediastinum is very unusual, but that possibility exists. Herein, we illustrate examples of this rare phenomenon.