Ultrasound characteristics of thyroid nodules facilitate interpretation of the malignant risk of Bethesda system III/IV thyroid nodules and inform therapeutic schedule.

Background This study was designed to explore whether ultrasound of thyroid nodules facilitates the interpretation of the malignant risk of Bethesda III/IV thyroid nodules to inform further therapies. Methods We reviewed patient records in which the results of ultrasound-guided fine-needle aspiration (US-FNA) were classified by the Bethesda III/IV in our institution between January 2016 and June 2018. Studies were retrieved from PubMed, Cochrane Central Register of Controlled Trials, ISI Web of Science, Science Direct, Wiley Online Library, EMBASE, China National Knowledge Infrastructure, WanFang, and Chinese VIP. The odds ratio (OR) was used to measure associations between risk factors and thyroid nodule malignancy. Results Fifty-nine cases of Bethesda III/IV with corresponding surgeries were included, and the malignancy risk was 54.2%. Meta-analysis revealed irregular borders, solitary nodules, hypoechogenicity, microcalcifications, and being taller than wide, all of which increased the malignancy risk of thyroid nodules. Combined ORs for these factors were 4.08 (95% CI: 2.34-7.14, P < .001), 2.18 (95% CI: 1.39-3.42, P = .001), 2.02 (95% CI: 1.35-3.01, P = .001), 3.21 (95% CI: 2.26-4.56, P < .001), and 4.35 (95% CI: 3.07-6.15, P < .001), respectively. Conclusion As the risk of malignancy for papillary thyroid carcinoma (PTC) is high, when any one of the five ultrasound features of malignancy were confirmed, repeated FNA is recommended to confirm PTC-type malignancy, even though nodules were Bethesda III/IV classification. However, repeated FNA should be avoided when none of these ultrasound features are identified because repeated FNA does not contribute to identifying non-PTC type malignancies, such as follicular thyroid carcinoma and poorly differentiated thyroid carcinoma.