Clinico-cytopathological subcategorization in thyroid nodules of atypia of undetermined significance/follicular lesion of undetermined significance using the TIRADS and Bethesda classifications

Abstract

IntroductionBethesda category III – atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) is a heterogeneous class of the Bethesda system for thyroid nodules. In order to clarify the therapeutic road for clinicians, this category was subclassified based on the cytopathological features. In this study, we evaluated the risk of malignancy, surgical outcome, demographic characteristics, and correlation of ultrasound features with the final outcome in patients with thyroid nodules based on AUS/FLUS subclassification.MethodAfter evaluating 867 thyroid nodules from three different centers, 70 (8.07%) were initially diagnosed as AUS/FLUS. The cytopathologists re-interpreted the FNA samples and subclassified them into five subcategories: architectural atypia, cytologic atypia, cytologic and architectural atypia, and Hürthle cell AUS/FLUS, and atypia, which was not specified. Based on the suspicious ultrasound features, an appropriate ACR TI-RADS score was allocated to each nodule. Finally, the malignancy rate, surgical outcomes, and ACR TI-RADS scores were evaluated among Bethesda category III nodules.ResultsAmong the 70 evaluated nodules, 28 (40%) were subclassified as Hürthle cell AUS/FLUS, 22 (31.42%) as cytologic and architectural atypia, 8 (11.42%) as architectural atypia, 7 (10%) as cytologic atypia, and 5 (7.14%) as atypia which was not specified. The overall malignancy rate was 34.28%, and the architectural atypia and Hürthle cell nodules displayed lower malignancy compared to other groups (P-Value<0.05). Utilizing ACR TI-RADS scores showed no statistical significance between Bethesda III subcategorization and ACR TI-RADS scores. However, ACR TI-RADS can be a reliable predictor for Hürthle cell AUS/FLU nodules.ConclusionACR TI-RADS helps evaluate malignancy only in the Hürthle cell AUS/FLUS subcategory of AUS/FLUS. Besides, cytopathological reporting based on the suggested AUS/FLUS subclassification could help clinicians take appropriate measures to manage thyroid nodules.

Pitfalls in Thyroid Fine-Needle Aspiration Cytopathology: An Approach to Atypical Findings

“…Several studies have compared the ROM in which FNAC samples were subdivided based on whether they exhibited nuclear and/or architectural atypia, in which combined nuclear and architectural atypia has the highest ROM and is often shown to represent PTC on the histologic follow-up. However, isolated nuclear atypia has a somewhat lower ROM, and the ROM for cases with architectural atypia is generally much lower [9,13,14]. A similar trend has also been observed in thyroid FNA specimens from pediatric patients, where it was observed that the nuclear atypia as opposed to architectural atypia exhibited a clear-cut association with malignancy [15].…”

“…1, 2) [1,[26][27][28]. The ROM for cases with architectural atypia in most instances is quite low, but not negligible [9,13,14].…”

A Comprehensive Approach to the Thyroid Bethesda Category III (AUS) in the Transition Zone Between 2nd Edition and 3rd Edition of The Bethesda System for Reporting Thyroid Cytopathology: Subcategorization, Nuclear Scoring, and More

“…On the other hand, the majority of these studies belong to the era before NIFTP and malignancy rates included NIFTP. However, in the post-NIFTP period, NIFTP is included in the malignant category in some of these studies [ 37 ], while in others, the status of NIFTP is not fully explained [ 16 , 26 , 38 , 47 ]. NIFTP was not even mentioned in several studies [ 8 , 25 , 48 ].…”