Intense accumulation of Tl-201 in carcinoid tumor of the thymus

A case of carcinoid tumor of the thymus is presented in which Tl-201 SPECT demonstrated intense accumulation in the lesion. Conventional chest radiograph and CT scan in a 66-year-old man who had been experiencing cough and pain at the anterior part of the chest revealed a tumor in the anterior mediastinum, suggesting a thymoma. The tumor was clearly delineated in both early and delayed SPECT studies. On the delayed scan, the tumor was more prominently visualized with an extremely high uptake ratio of the lesion compared to the contralateral background; therefore, the tumor was believed to possess very prolonged Tl-201 retention. The pathological and immunohistochemical examinations confirmed that the area of intense Tl-201 uptake was rich in viable cells.