Nonsuppressing normal thymus on chemical shift magnetic resonance imaging in a young woman

A previously healthy 21-year-old woman presented with syncope and arrhythmia. A computed tomographic coronary angiogram was solely remarkable for an anterior mediastinal mass. Mediastinal magnetic resonance imaging of the reported mass revealed mildly prominent thymic tissue for age, with no suppression on out-of-phase chemical shift magnetic resonance imaging. Thymoma and lymphoma could not be excluded. After diagnosis and stabilization of her arrhythmia, the patient underwent median sternotomy and radical thymectomy, with pathology revealing normal thymus. This case suggests that nonsuppression of mildly prominent, homogenous thymic soft tissue in young women may not be sufficient to warrant diagnostic intervention and instead may warrant close follow-up.