Riedel's thyroiditis is an extremely rare disease that is difficult to diagnose correctly using preoperative diagnostic tools because it can mimic malignant neoplasm or the fibrous variant of Hashimoto thyroiditis during preoperative physical, radiologic, and pathologic examination. We describe here a rare case of Riedel's thyroiditis in an elderly patient and its radiologic characteristics.
Keywords: Magnetic resonance imaging; Positron-emission tomography; Riedel's thyroiditis; Ultrasonography; X-ray computed tomography.