Classification of mediastinal compartments: is separation of the superior mediastinum crucial?-a clinical practice review.

Abstract

The division of the mediastinum into specific compartments is essential for identifying, characterizing, and managing mediastinal abnormalities. The current international standard is the three-compartment model proposed by the International Thymic Malignancy Interest Group (ITMIG), which divides the mediastinum into prevascular (anterior), visceral (middle), and paravertebral (posterior) compartments. This model has replaced the traditional four-compartment system, which included the superior mediastinum, due to its simplicity, familiarity, and clearly defined boundaries. However, given the superior mediastinum's unique anatomy and distinct pathology, it remains clinically reasonable to consider it separately. Continued clinical use of the term "superior mediastinum" has produced numerous conflicting definitions, while the Japanese Association for Research on the Thymus (JART) has recently proposed a computed tomography (CT)-based four-compartment model. Disease distribution in the superior mediastinum is dominated by thyroid goiters and neurogenic tumors, while the incidence of thymic epithelial tumors (TETs) in this region varies among studies. Surgery in the superior mediastinum is challenging due to its narrow space and the presence of major blood vessels and nerves. Operative complications frequently include Horner's syndrome. Furthermore, studies suggest that superior mediastinal thymomas may demonstrate more aggressive behavior and lower survival rates than thymomas in other locations. Establishing a clear, standardized definition of the superior mediastinum would resolve current inconsistencies and facilitate the accumulation of detailed clinical data on superior mediastinal lesions. This article focuses on the superior mediastinum and discusses its classification, clinical features, surgical approaches, treatment outcomes, and future perspectives.