Imaging of a case of metaplastic thymoma on 18F-FDG PET/CT.

Metaplastic thymoma is a rare primary thymic epithelial tumor. This report presents the 18F-FDG PET/CT appearance of a metaplastic thymoma developed in a 61-year-old female patient. The FDG uptake of the mediastinal mass showed a high maximum SUV, thus suggesting the possibility of thymic cancer. Surgical resection was performed for both a definitive diagnosis and treatment of the mediastinal tumor. A histological examination of the resected specimen revealed metaplastic thymoma. Although rare, thymoma should be carefully considered in the differential diagnosis in cases of mediastinal masses presenting with highly positive findings on 18F-FDG PET/CT to avoid any inappropriate patient management.