Thymic infarcts are rare, and mainly occur following an occlusive event of stromal vessels. Distinguishing thymic infarcts from anterior mediastinal masses is important due to different treatment plans and prognoses. We describe an unusual case of a thymic infarct in a patient with the sudden onset of chest pain. In this case, FDG PET revealed central photon defects with uptake in a peri-rim-shaped lesion in the anterior mediastinum. A chest CT showed a poorly marginated anterior mediastinal mass with a small calcified lesion. An anterior mediastinal mass resection was performed. The histopathologic finding was a thymoma with an infarction.