Diagnostic approach to the anterior/prevascular mediastinum for radiologists

The mediastinum contains vital vascular and nonvascular organs and other structures, and a wide variety of neoplasms and other abnormalities may originate from this anatomic region of the chest. Division of the mediastinum into distinct compartments helps narrow the differential diagnosis of mediastinal abnormalities detected on imaging studies, assists the planning of biopsy and surgical procedures, and facilitates communication between healthcare providers in the multidisciplinary setting. Numerous different models have been developed and used by radiologists, surgeons, and anatomists. Recently, the International Thymic Malignancy Interest Group (ITMIG) developed a new classification model of the mediastinal compartments based on cross-sectional imaging that has been accepted as a new standard. Although mediastinal pathology may be first identified on chest radiographs, cross-sectional imaging techniques such as computed tomography (CT) and magnetic resonance (MR) imaging play critical roles in the identification, localization, and characterization of mediastinal lesions. CT is considered the imaging modality of choice to evaluate most masses; however, MR imaging is superior to CT in differentiating between cystic and solid lesions, identifying cystic and solid components within complex masses, and distinguishing thymic hyperplasia and normal thymus from thymic epithelial neoplasms and other neoplasms. In this article, the new ITMIG classification of mediastinal compartments is presented along with approaches to the imaging evaluation of masses in the anterior/prevascular mediastinum.