Usefulness of Thallium-201 Scintigraphy for Differentiating Benign and Malignant Thyroid Nodules in Inconclusive Cases with Fine Needle Aspiration / 대한내분비학회지

ABSTRACT

BACKGROUND: Although fine needle aspiration(FNA) is recognized as the most accurate procedure in the differential diagnosis of thyroid nodules, about 20~30% of nodules remain inconclusive in FNA. Therefore, we assessed the usefulness of Thallium-201 scintigraphy in differentiating benign from malignant thyroid nodules in patients with inconclusive diagnosis by FNA. METHODS: We studied 43 patients with inconclusive diagnosis(29 of follicular neoplasm, 11 of cystic change and 3 of inadequate) by FNA, with the results being confirmed histopathologically by operation. Thallium-201 scintigraphy was performed at 15 minutes(early scan) and 2-3 hours(late scan) after the intravenous administration of 37 MBq of thallium-201. Malignant nodules were defined by the retention of Thallium-201 on delayed images. RESULTS: In the 43 patients with inconclusive FNA diagnosis, Thallium-201 scan had a sensitivity of 75.0%, specificity of 62.9% and accuracy of 65.1%. The positive and negative predictive values were 31.6% and 91.7%, respectively. In the 29 patients with follicular neoplasm by FNA, Thallium-201 scan had a sensitivity of 83.3%, specificity of 60.9% and accuracy of 65.5%. The positive and negative predictive values were 35.7% and 93.3%, respectively. CONCLUSION: In particular, Thallium-201 scintigraphy demonstrated a high negative predictive value, Therefore, for patients with inconclusive FNA findings, Thallium-201 scintigraphy might be useful in differentiating between benign and malignant thyroid nodules, and has the potential to reduce the rate of unnecessary operations in benign nodules.