Thymic tuberculosis preoperatively evaluated with thallium-201 SPECT: two resected cases

We present 2 resected cases of thymic tuberculosis, which had been preoperatively diagnosed as invasive thymoma, using a thallium-201 ((201)Tl) single photon emission computed tomography ((201)Tl SPECT). [Patient 1] A 74-old-male with a 32-year history of steroid therapy for rheumatic arthritis was diagnosed with an anterior mediastinal tumor by routine chest CT scans after onset of myocardial infarction. [Patient 2] A 56-old-female with a 28-year history of diabetes mellitus presented with a dry cough. A chest CT demonstrated an anterior mediastinal tumor. Neither patient showed pulmonary infiltrations on chest x-ray. (201)Tl SPECT was undertaken for each patient. Abnormal findings could not be detected on a planar image of the scintigraphy; however, on SPECT images accumulations of (201)Tl were clearly detected in the anterior mediastinal mass and a thymoma was thus suspected in each case. Total thymectomy was carried out in each case and the mass then diagnosed as caseous granuloma in the thymus. Both patients are well without recurrence after operation. In patients with a (201)Tl SPECT positive anterior mediastinal tumor associated with an immunologically deficient status, and with negative findings in planar images on thallium scintigraphy, the possibility of thymic tuberculosis should be considered.