Ultrasound Risk Categories for Thyroid Nodules and Cytology Results: A Single Institution's Experience after the Adoption of the 2016 Update of Medical Guidelines by the American Association of Clinical Endocrinologists and Associazione Medici Endocrinologi.

Objectives: In 2016, the American Association of Clinical Endocrinologists (AACE) and Associazione Medici Endocrinologi (AME) released updated guidelines for the diagnosis and management of thyroid nodules. The aim of this study was to evaluate the AACE/AME recommendations for FNA in clinical practice, by comparing the (US) stratification risk and indications for FNA with cytologic results.

Methods: From May to December 2016, we collected the cytologic results from FNAs of nodules that were classified using a three-tier US category system (low, intermediate, and high risk).

Results: We obtained 859 FNAs from 598 patients: 341 (39.7%) from low, 489 (56.9%) from intermediate, and 29 (3.4%) from high risk nodules. Of these, 88.5% and 74.9% of low and intermediate risk nodules, respectively, were cytologically benign, whereas 84.6% of high risk nodules had a moderate-to-elevated risk of malignancy or were malignant. If FNAs had been limited to intermediate risk nodules >20 mm, we would have missed 13/17 (76.5%) nodules that had moderate-to-elevated risk of malignancy or were malignant (11/13 were malignant based on histology).

Conclusions: A nonnegligible number of cytologically malignant nodules or nodules that were suspected to be malignant would be missed if intermediate US risk nodules <20 mm were not biopsied.