Utility of I-123 thyroid uptake scan in incidental thyroid nodules: an old test with a new role.

Abstract

In an incidentally discovered multinodular thyroid goiter, determining which nodule to biopsy is challenging. This study examined whether I-123 thyroid uptake scans (TUS) could guide this biopsy. A retrospective review of 71 patients referred for evaluation of an incidentally discovered thyroid nodule was conducted. Patients with a multinodular thyroid underwent I-123 TUS. Of 71 patients, 14 had multinodular thyroids. Average number of nodules per patient was 5.3 with an average size disparity between nodules of only 0.4 cm. TUS found an isolated "cold" nodule in 9 of 14 (64%) patients. "Cold" nodules represented cancer by biopsy or surgical pathology in 3 of 9 (33%) patients. A normal or "hot" TUS corresponded to benign pathology in 5 of 5 (100%) patients. This gave a "cold" nodule 100% sensitivity for finding cancer in a thyroid nodule, and a specificity of 45%. Of patients referred for evaluation of an incidentally discovered thyroid nodule, 20% had multinodular disease. I-123 TUS have generally been removed from the treatment algorithm of thyroid nodules owing to the reliability of fine-needle aspiration biopsy. However, in the setting of a multinodular goiter, this test demonstrated utility by decreasing unnecessary, multiple biopsies in 71% of patients. This old test has gained a new role in the management of these challenging cases.