Posterior Mediastinal Mass With Intracardiac Protrusion: A Diagnostic Conundrum Resolved With Multimodality Imaging

Posterior mediastinal masses are rare and remain asymptomatic until they enlarge enough to compress vital vascular structures, the tracheobronchial tree, the spine, or cardiac chambers. Computed tomography (CT) and cardiac magnetic resonance (CMR) provide precise locations and characterization of lesions.

A young woman was found to have a cystic mass in the posterior mediastinum extending into the interatrial septum and left atrium (LA) on echocardiography. Cardiac CT and CMR showed it protruding into the interatrial septum and LA. The diagnosis was confirmed as hydatid cyst on imaging and histopathologic examination.

Mediastinal hydatid cysts are usually asymptomatic but may rarely cause pressure effects on vital organs or rupture, leading to life-threatening complications mandating precise diagnosis and management.

Primary posterior mediastinal hydatid cysts are uncommon and can protrude into cardiac chambers, simulating a cardiac mass on echocardiography. They can be accurately diagnosed using multimodality imaging to guide appropriate treatment.