• Kwang Hwi Lee, Jung Hee Shin, Young Lyun Oh, and Soo Yeon Hahn.
• Department of Radiology and Center for Imaging Science, Thyroid Center, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Irwon-dong, Gangnam-gu, Seoul, 135-710, Korea.
• Ann. Surg. Oncol. 2014 Jul 1;21(7):2326-31.

BackgroundFurther management for thyroid nodules with cytological atypia of undetermined significance (AUS) has made controversial conclusions. The aim of this study was to evaluate the most reliable ultrasonography (US) findings to predict malignancy in thyroid nodules with AUS, and to compare inconclusive rates of repeat fine-needle aspiration (rFNA) and core needle biopsy (CNB) in nodules with AUS.MethodsWe retrospectively reviewed cases of thyroid nodules with AUS from 8,421 US-guided fine-needle aspirations in our institution between 2010 and 2012. Nodules were confirmed either surgically or followed-up for at least 1 year and were compared based on nodule size, US findings, and US diagnosis to predict malignancy. Inconclusive rates of rFNA and CNB after initial AUS were compared.ResultsThe incidence of AUS in all thyroid nodules was 3.2 % (273 of 8,421). Malignancies were identified in 42.1 % (64 of 152) nodules with surgery or sufficient follow-up. In univariate analysis, not-oval to round shape, irregular margin, taller-than-wide orientation, hypoechogenicity, marked hypoechogenicity, microcalcifications, and malignant US diagnosis were more frequent in actual malignancies (p < 0.05). In multivariate analysis, hypoechogenicity, marked hypoechogenicity, and malignant US diagnosis were significantly more frequent in malignancies (p < 0.05). With respect to further management of AUS, the inconclusive rate of CNB (17.6 %, 6/34) was significantly lower than that of rFNA (37.3 %; 44 of 118) (p = 0.032).ConclusionsNodule echogenicity and US diagnosis can be predictive factors of malignancies for the thyroid nodules with cytological AUS. The CNB is more useful than rFNA for reducing the frequency of inconclusive results after initial AUS.

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