CTICasesThymic Cyst Mimicking a Solid Mediastinal Mass
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Imaging findings
An anterior mediastinal lesion with smooth, round margins was observed over several years, initially appearing solid with CT attenuation values in the 30s-40s Hounsfield Units. It was described as potentially increasing in size. A CT-guided biopsy showed the aspiration of milky fluid, and the lesion subsequently appeared smaller and 'squashed' on post-aspiration images, confirming its cystic nature. No malignant cells were found.
Key takeaways
This case illustrates a diagnostic pitfall where thymic cysts can mimic solid mediastinal masses on CT, particularly if their contents (protein, blood) result in higher-than-water attenuation values. Percutaneous aspiration can be both diagnostic and therapeutic, confirming the cystic nature and leading to resolution.
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