The role of radiological imaging for masses in the prevascular mediastinum in clinical practice

Tumors in the prevascular compartment of the mediastinum are rare and imaging plays a major role in their detection, (differential) diagnosis, staging, and follow-up. The prevascular compartment is bordered anteriorly by the posterior aspect of the sternum, posteriorly by the ventral aspect of the pericardium, cranially by the thoracic outlet, and caudally by the diaphragm. In many cases, the diagnosis of a lesion in the prevascular compartment is an incidental finding either on chest radiograph (CR) or on computed tomography (CT) scans. The differential diagnosis of masses in the pre-vascular mediastinum include primarily tumors arising from the thymus or the thyroid gland, lymphomas and germ cell tumors. The differential diagnosis of mediastinal masses is primarily based on the location of the mass, its tissue composition (i.e., fat content, calcifications) and the age of the patient. The imaging method of choice is CT, as it combines a high spatial and temporal resolution with the ability to determine tissue composition and detect fluid components, as well as areas of fat and calcifications. MRI is used as a more specific problem-solving tool to discriminate solid lesions from cystic lesions or to provide evidence of minimal fat content in teratoma and thymic rebound. The role of PET/CT in the evaluation of tumors other than lymphomas in the prevascular compartment is still under discussion.