A Rare Cause for a Mediastinal Lesion

The term “mediastinum” refers to a tissue compartment that resides between the 2 lungs, posterior to the sternum, anterior to the spine, and extending from the thoracic inlet to the diaphragm. A great number of structures reside within this region, any of which can give rise to a wide variety of abnormalities. Lesions arising within the mediastinum often defy easy classification, owing to the complex anatomy of the region. By convention, the mediastinum is divided into 3 compartments: anterior (prevascular), middle (visceral), or posterior (paravertebral) compartments. Each compartment contains certain structures that may give rise to particular pathologies, and hence the compartmental approach for mediastinal lesion localization at imaging is often quite useful for generating differential diagnoses when abnormalities are encountered. Uncommonly, certain lesions arise within the mediastinum for which the histopathology cannot be predicted on the basis of localization of the lesion using the compartmental approach. In this case, a correct diagnosis may be considered if a particular clinical context or imaging characteristics are present that point to a single diagnosis, but, if such specific indicators are lacking, the correct diagnosis may only be established through invasive tissue sampling procedures.