F-18 FDG PET/CT demonstration of thymoma followed by development of lung cancer

It is well-known that thymoma can be associated with diverse extrathymic malignancies. The authors present a case of a 72-year-old man with myasthenia gravis in which F-18 FDG PET/CT demonstrated high FDG uptake in both an anterior mediastinal mass and a lung nodule. The FDG uptake in the lung nodule was significantly higher than that of the thymic lesion, which might suggest the possibility of a second development of lung cancer in this thymoma patient. Surgical resection was done for the 2 tumors, and histologic examination revealed anterior mediastinal thymoma and primary adenocarcinoma of the lung. This case demonstrates the potential usefulness of PET/CT in detecting and assessing the second extrathymic malignancy in a patient with thymoma.