A 64-year-old man was hospitalized for examination of a neck tumor. A computed tomographic (CT) scan showed a thyroid tumor, including calcification and cystic changes in the right lobe, and soft tissue density masses were seen in the neck and mediastinum. Tc-99m pertechnetate imaging showed a defect in the area corresponding to the mass seen on CT. TI-201 imaging showed marked accumulation in the mass both in the early and delayed images. On Ga-67 imaging, there was accumulation comparable to that seen with TI-201 in the same area. Surgical biopsy revealed that the tumor was squamous cell carcinoma. Because no other primary lesion was detected, the lesion was thought to be thyroid in origin.