CTICasesMediastinal Teratoma Mimicking Pericardial Cyst
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Imaging findings
Chest radiograph and lateral projection demonstrate a large, smooth-bordered, rounded mass in the right aspect of the mediastinum. On CT, the lesion appears as a well-defined, simple fluid-attenuating cyst measuring around 10 Hounsfield units (ranging between -30 and 50 Hounsfield units), associated with regional mass effect on the heart and mild wall thickening. Cardiac MRI reveals a complex, heterogeneous mass with areas of high, low, and intermediate signal on T1- and T2-weighted imaging, some of which demonstrate signal loss on post-contrast fat-saturated images.
Key takeaways
Mediastinal teratomas can mimic benign pericardial cysts on CT when they exhibit predominantly fluid attenuation. However, features such as wall thickening, mass effect on the heart, or subtle heterogeneity should raise suspicion for a more complex lesion. Cardiac MRI is a powerful problem-solving tool to characterize the true complexity, septations, or lipid components of cystic mediastinal masses, helping to differentiate teratomas or cystic thymomas from simple pericardial cysts.
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