Indications for Core Needle Biopsy in Low-Suspicion Thyroid Nodules on US.

PURPOSE: This study aimed to identify the appropriate clinical indications for core needle biopsy (CNB) in low-suspicion nodules (Korean Thyroid Imaging Reporting and Data System category 3) by assessing the US features associated with CNB-based diagnoses of malignancy and surgically relevant disease. MATERIALS AND METHODS: Between January 2018 and December 2019, 910 thyroid nodules from 903 patients underwent US-guided CNB. Among these, 271 patients with low-suspicion thyroid nodules on US who later underwent surgery were included in this study. The nodules were dichotomized into two categories: malignancy (including low-suspicion neoplasms) and surgical disease (categorized as follicular neoplasm, suspicious for malignancy, or malignancy on CNB). Hypervascularity was defined as types 3 or 4. RESULTS: The malignancy rate of resected low-suspicion nodules was found to be 36.5%. In low-suspicion nodules, a well-defined halo and hypervascularity were independent risk factors associated with malignancy (odds ratio = 2.06, 95% confidence interval [CI] = 1.11-3.83, p = 0.02 for well-defined halo; odds ratio = 3.54, 95% CI = 1.96-6.38, p < 0.01 for hypervascularity) and surgical disease (odds ratio = 4.96, 95% CI = 2.66-9.24, p < 0.01 for well-defined halo; odds ratio = 2.98, 95% CI = 1.96-6.38, p < 0.01 for hypervascularity). When the two features were combined, the diagnostic area under the receiver operating characteristic curve was 0.660 for malignancy and 0.709 for surgical disease. CONCLUSION: Targeting low-suspicion thyroid nodules with a well-defined halo and hypervascularity observed on US may provide supplementary diagnostic value in identifying nodules associated with malignancy and surgical disease using CNB.