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BackgroundAtypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) is one of six diagnostic categories of The Bethesda System for Reporting Thyroid Cytopathology (BSRTC). The goal of our study is to assess the outcome of cases classified as AUS/FLUS at our institution.MethodsAUS/FLUS cases were identified by computer searching of the thyroid fine‐needle aspiration (FNA) cases performed between 2010 and 2016. Outcomes were categorized as: follow‐up surgery, repeat FNA or no follow‐up available. Demographics, ultrasound findings and FNA diagnostic criteria were reviewed for AUS/FLUS cases with follow‐up surgical pathology diagnosis.ResultsOur AUS/FLUS thyroid FNA rate was 6% (117 out of 1984 FNAs). Only 15% of the AUS/FLUS cases had repeat FNA, while 41% underwent surgery. The risk of malignancy (ROM) for cases with follow‐up surgery was 17%. When considering all AUS/FLUS cases, the ROM was 7%. Statistically, benign neoplasms were more likely to be single lesions on ultrasound comparing to malignant neoplasms, and to exhibit architectural atypia as opposed to non‐neoplastic lesions on FNA. The malignancy rates among patients that directly went to surgical resection (17%) and patients having repeat FNA after the first AUS/FLUS diagnosis followed by surgery (29%) was not significantly different. However, repeat FNA was able to reclassify the majority of cases into more definitive categories.ConclusionThe outcome of the thyroid FNAs diagnosed as AUS/FLUS in our institution meets the benchmark statistics for AUS/FLUS rate and ROM. This study constitutes a valuable quality assurance measure and serves as a baseline for subsequent quality improvement.