Young investigator challenge: Atypia of undetermined significance in thyroid FNA: Standardized terminology without standardized management—a closer look at repeat FNA and quality measures

Abstract

BACKGROUND:The Bethesda system (TBS) for the reporting of thyroid cytopathology established the category of atypia of undetermined significance (AUS) with a 7% target rate and a 5% to 15% implied malignancy risk. Recent literature has reported a broad range of AUS rates, subsequent malignancy rates, and discrepant results from repeat fine-needle aspiration (FNA) versus surgical follow-up. Therefore, this study examined AUS data from the Hofstra North Shore-LIJ School of Medicine to determine the best clinical follow-up. METHODS: Thyroid aspirates interpreted as AUS in 2012-2014 at the Hofstra North Shore-LIJ School of Medicine were collected. Repeat FNA and surgical follow-up data were tabulated to establish AUS, secondary AUS (diagnosed upon repeat FNA follow-up of a primary FNA AUS diagnosis), atypia of undetermined significance/malignancy (AUS:M) ratios (according to the TBS categories), and malignancy rates for AUS. RESULTS:The AUS rate was 8.5% (976/11,481), and there was follow-up data for 545 cases. The AUS:M ratio was 2.0.Repeat FNA was performed for 281 cases; 57 proceeded to surgical intervention. Repeat FNA reclassified 71.17% of the cases. The malignancy rates for AUS cases proceeding directly to surgery and for those receiving a surgical intervention after a repeat AUS diagnosis were 33.33% and 43.75%, respectively. CONCLUSIONS: Repeat FNA resulted in definitive diagnostic reclassification for 67.61% of primary AUS cases and reduced the number of patients triaged to surgery, with 56.58% of the cases recategorized as benign. Cases undergoing surgery after repeat AUS had a higher malignancy rate than those going straight to surgery, and this emphasizes the value of repeat FNA in selecting surgical candidates. In addition, this study highlights the utility of AUS rate monitoring as a quality measure that has contributed to the ability of the Hofstra North Shore-LIJ School of Medicine to adhere closely to TBS recommendations. Cancer (Cancer Cytopathol) 2016;124:37-43.

The impact of repeat FNA in non‐diagnostic and indeterminate thyroid nodules: A 5‐year single‐centre experience

“…Mirroring the results for the non‐diagnostic cases, the majority of our AUS/FLUS cases were reclassified as benign, reaching a definite diagnosis in 75% of the cases. This is also in agreement to the literature, showing a definition of diagnosis in repeat FNA from around 50% to 90% of cases . Hence, it is not surprising that most molecular signatures that are in use and being developed for indeterminate cases aim at a high sensitivity and negative predictive value, searching for cases inadvertently operated with a final benign diagnosis .…”

Thyroid nodules classified as atypia or follicular lesions of undetermined significance deserve further research: Analysis of 305 surgically confirmed nodules

“…However, similar to previous findings, the malignancy rate of our study was much higher than the NCI‐expected rate for the AUS/FLUS category . Owing to the use of clinical or radiological risk factors in the decision‐making process and considering that only nodules with a higher risk for malignancy were referred to surgery, “selection bias” may have unintentionally occurred in any evaluation . Additionally, as was shown in the present study, some groups of nodules diagnosed as benign after FNA were confirmed to be malignant in the postsurgical evaluation.…”

Evaluation of BRAF, RAS, RET/PTC, and PAX8/PPARg alterations in different Bethesda diagnostic categories: A multicentric prospective study on the validity of the 7‐gene panel test in 1172 thyroid FNAs deriving from different hospitals in South Italy

“…However, because repeated FNAs are usually recommended for AUS/FLUS, in this study, we considered FNA repetition as a valid endpoint only when the repeated cytology outcome was benign. A similar approach has already been suggested by Brandler et al and Eszlinger et al for the audit of their FNA series. By contrast, cases with a persistent AUS/FLUS diagnosis or those featuring TBSRTC classes with a higher ROM but without an available histologic diagnosis were excluded.…”