Low reproducibility of equivocal categories of the Bethesda System for Reporting Thyroid Cytology makes the associated risk of malignancy specific to the diagnostic center

Dorota Słowińska-Klencka,Joanna Duda-Szymańska,Bożena Popowicz,Mariusz Klencki,Jarosław Szwalski

doi:10.1007/s12020-021-02781-3

Dorota Słowińska-Klencka, Joanna Duda-Szymańska + Show 3 more

Open Access

https://doi.org/10.1007/s12020-021-02781-3

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Journal: Endocrine	Publication Date: Jun 12, 2021
Citations: 9	License type: open-access

Affiliation: Medical University of Lodz

Abstract

PurposeEquivocal categories (III, IV, V) of the Bethesda System for Reporting Thyroid Cytology (BSRTC) are characterized by high variability of the estimated risk of malignancy. The aim of the study was to analyze the reproducibility of classification of nodules into an equivocal category and the frequency of malignancy (FoM) observed in such categories.MethodsFive experienced cytopathologists from three centers (A, B, C) independently performed reclassification of smears obtained from 213 thyroid nodules with equivocal routine cytology and known results of the postoperative histopathological examination.ResultsThe interobserver agreement among all cytopathologists was poor, with a Krippendorff’s alpha coefficient equaling 0.34. The intra-center agreement was higher than the inter-center (fair vs poor). Pathologists of the center A classified smears into categories II and III significantly less often and categories IV and V more often than pathologists of centers B and C. The joint FoM of nodules classified into any of categories IV–VI (regarded as an indication for surgery) was different among centers (A: 40.0%, B: 66.7%, C: 80.6%). The FoM of category III nodules with features of nuclear atypia (AUS) in center B and C was two times higher than that of other nodules of category III (FLUS), while in center A the FoM was similar.ConclusionsThe use of published data on the risk of malignancy in nodules of particular BSRTC categories without concern for the uniqueness of the diagnostic center may lead to erroneous conclusions.

Highlights

The diagnostics of thyroid nodules is challenging
The category V—the suspicion of malignancy (SM)—is commonly regarded as an indication for surgical treatment because of the high risk of malignancy (RoM): amounting to 45–75%, according to the authors of the Bethesda System for Reporting Thyroid Cytology (BSRTC) (45–60% if the diagnosis of non-invasive follicular thyroid neoplasm with papillary-like nuclear features -NIFTP is regarded as a benign lesion and 50–75% if it is regarded as a malignancy), and even reaching 90%, according to some reports [1,2,3,4]
The category IV—the suspicion of follicular neoplasm (SFN)/suspicion of Hürthle cell tumor (SHT)—is related to the lower RoM (10–40 or 25–40% depending on the interpretation of NIFTP as a benign or malignant lesion, respectively), according to the authors of the BSRTC, but it Endocrine (2021) 74:355–364 is regarded as an indication for thyroid surgery [1,2,3,4]

Summary

Introduction

The category IV—the suspicion of follicular neoplasm (SFN)/suspicion of Hürthle cell tumor (SHT)—is related to the lower RoM (10–40 or 25–40% depending on the interpretation of NIFTP as a benign or malignant lesion, respectively), according to the authors of the BSRTC, but it Endocrine (2021) 74:355–364 is regarded as an indication for thyroid surgery [1,2,3,4]. In such cases, diagnostic uncertainties about nodule’s malignancy are usually dispelled only by the postoperative histopathological examination. Follicular-patterned cases with mild nuclear changes can be classified into the category IV as long as true papillae and intranuclear pseudoinclusions are absent [2]

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