Middle mediastinal mass lesions: Good, bad and ugly.

Abstract

Learning objectives: To present the imaging findings of four pathologically different mediastinal mass lesions with similar appearance on chest X-ray (CXR) and discuss how to overcome their differential diagnostic dilemma. Background: Primary mediastinal masses are a diverse group of lesions which present a diagnostic challenge to radiologists. A thorough understanding of mediastinal anatomy is essential for evaluation of a mediastinal mass, since specific lesions have a predilection for certain sites. Many mediastinal masses are serendipitously discovered on chest radiographs obtained for other reasons, but some patients will come to clinical attention with vague chest complaints or with signs and symptoms related to compression or invasion of mediastinal structures. Imaging findings: We are presenting four patients who showed a similar finding of a well-defined right paratracheal mass lesion on their CXRs but after further investigations with cross-sectional imaging and biopsy, different diagnoses of Bronchogenic Cyst (Good), Mediastinal nodal angiomatosis (Good), Benign Schwannoma (Bad) and Thrombosed Superior Vena Cava (Ugly) were established. Unique imaging clues of these cases were: * Punctate calcifications in Schwannoma, * Fluid density of bronchogenic cyst, * Heterogeneous enhancing lesion with stable size and density on serial CTs and high intensity on T2 weighted sequences with early and prolonged diffuse inhomogeneous enhancement on dynamic Magnetic resonance images (MRI) of Nodal Angiomatosis * Continuity of thrombosed Superior Vena Cava (SVC) with SVC. Conclusion: Although a routine CXR often initiates the evaluation of mediastinal disorders, it is rarely diagnostic. The most conclusive ensuing cross sectional imaging is spiral CT, providing important information about anatomic location, extent of disease, tissue invasion and tissue density. MRI is superior to Spiral CT for imaging nerve plexus, for distinguishing tissue planes and invasion, and imaging in non transaxial planes. However, occasionally tissue biopsy is required for definite diagnosis, as depicted in the examples shown.<br />