Malignancy Risk for Fine-Needle Aspiration of Thyroid Lesions According to The Bethesda System for Reporting Thyroid Cytopathology

Abstract

Fine-needle aspiration (FNA) is an important test for triaging patients with thyroid nodules. The 2007 National Cancer Institute Thyroid Fine-Needle Aspiration State-of-the-Science Conference helped instigate the recent publication of The Bethesda System for Reporting Thyroid Cytopathology. We reviewed 3,080 thyroid FNA samples and recorded interpretations according to the proposed standardized 6-tier nomenclature, and pursued follow-up cytology and histology. Of the 3,080 FNAs, 18.6% were nondiagnostic, 59.0% were benign, 3.4% were atypical follicular lesion of undetermined significance (AFLUS), 9.7% were "suspicious" for follicular neoplasm (SFN), 2.3% were suspicious for malignancy (SM), and 7.0% were malignant. Of 574 cases originally interpreted as nondiagnostic, 47.9% remained nondiagnostic. In 892 cases, there was follow-up histology. Rates of malignancy were as follows: nondiagnostic, 8.9%; benign, 1.1%; AFLUS, 17% (9/53); SFN, 25.4%; SM, 70% (39/56), and malignant, 98.1%. Thus, classification of thyroid FNA samples at the University of Virginia Health System, Charlottesville, according to The Bethesda System yields similar results for risk of malignancy as reported by others. Universal application of the new standardized nomenclature may improve interlaboratory agreement and lead to more consistent management approaches.

The atypia of undetermined significance/follicular lesion of undetermined significance:malignant ratio

“…5,6,8,9,[12][13][14] The data from these series are summarized in Table 1. It is interesting to note that the overall rate of AUS was 9.7% with only 2 of 8 series reporting AUS rates below the previously recommended threshold of 7%.…”

“…We identified PubMed-indexed, peer-reviewed published laboratory experiences using TBS in which the categorical breakdown of all 6 reporting tiers was identified 5,6,8,9,[12][13][14] and supplemented those data with previously unpublished figures from the Massachusetts General Hospital compiled by one of the authors (W.C.F.) from 2006 to 2008 using TBS (a subset of these cases was included in a prior study 3 ).…”

“…The first group is comprised of laboratories with an AUS:M ratio of 1. These laboratories are characterized by low AUS rates (Jo et al 5 and Theoharis et al 13 ) or a high M rate (Kim et al 6 ). The study by Kim et al 6 also had a high AUS rate but this did not offset the effect of the outlier M rate referred to previously.…”

“…The heterogeneity of this low-risk category inevitably means that there will be differences in its utilization with significant variability in AUS rates noted among individual practitioners as well as between laboratories. [2][3][4][5][6][7][8][9][10][11][12][13][14] Indeed, TBS only recommends a broad use range for each diagnostic category. 1 To promote uniform practice among laboratories and cytopathologists and encourage quality improvement, it is desirable to have performance measures associated with TBS, especially with regard to the AUS category.…”

“…15 The only such recommendation that accompanied TBS for thyroid cytopathology was that the AUS rate not exceed 7% 1 ; however, this proposal lacked a robust evidentiary basis and has proved to be unrealistic for many laboratories publishing their initial experiences with TBS. [2][3][4][5][6][7][8][9][10][11][12][13][14] In this study, we review the initial published experiences with AUS and TBS in conjunction with our own laboratory experiences, with the goal of identifying evidencebased performance measures that will have usefulness in measuring individual and laboratory practices. In so doing, we hope to provide a basis for quality improvement in the reporting of thyroid aspirates within TBS framework.…”