Focally Increased Iodine Activity in a Small Thymic Cyst

: A 40-year-old man with biopsy-proven papillary thyroid cancer received I radiotherapy. Posttherapy scan showed not only multiple foci of intense activity in the neck but also a small focal activity in the region of right upper mediastinum, confirmed by SPECT/CT images. This activity was suspected as mediastinal lymph node metastasis. However, pathology examination after the resection showed thymic cyst.