Abstract
BackgroundCytologically indeterminate thyroid nodules currently present a challenge for clinical decision-making. The main aim of our study was to determine whether the classifications, American College of Radiology (ACR) TI-RADS and 2015 American Thyroid Association (ATA) guidelines, in association with The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC), could be used to stratify the malignancy risk of indeterminate thyroid nodules and guide their clinical management.MethodsThe institutional review board approved this retrospective study of a cohort of 140 thyroid nodules in 139 patients who were referred to ultrasound-guided fine-needle aspiration cytology (FNAC) from January 2012 to June 2016 with indeterminate cytological results (44 Bethesda III, 52 Bethesda IV and 44 Bethesda V) and in whom pre-FNAC thyroid US images and histological results after surgery were available. Each included nodule was classified by one radiologist blinded to the cytological and histological diagnoses according to the ACR TIRADS scores and the US patterns as recommended in the 2015 ATA guidelines. The risk of malignancy was estimated for Bethesda, TI-RADS scores, ATA US patterns and their combination.ResultsOf the 140 indeterminate thyroid nodules examined, 74 (52.9%) were histologically benign. A different rate of malignancy (p < 0.001) among Bethesda III, IV and V was observed. The rate of malignancy increased according to the US suspicion categories (p < 0.001) in both US classifications (TI-RADS and ATA). Thyroid nodules classified as Bethesda III and the lowest risk US categories (very low, low and intermediate suspicion by ATA and 2, 3 and 4a by TI-RADS) displayed a sensitivity of 95.3% for both classifications and a negative predictive value of 94.3 and 94.1%, respectively. The highest risk US categories (high suspicion by ATA and 4b,4c and 5 by TI-RADS) were significantly associated with cancer (odds ratios [ORs] 14.7 and 9.8, respectively).ConclusionsUltrasound classifications, ACR TI-RADS and ATA guidelines, may help guide the management of indeterminate thyroid nodules, suggesting a conservative approach to nodules with low-risk US suspicion and Bethesda III, while molecular testing and surgery should be considered for nodules with high-risk US suspicion and Bethesda IV or V.
Highlights
Indeterminate thyroid nodules currently present a challenge for clinical decision-making
Our study aims to stratify the malignancy risk of indeterminate Thyroid nodules (TNs) (Bethesda III, IV and V) by combining the cytology and US features correlating with the final histopathology from 139 thyroidectomized patients
TNs were included in this study if they had (a) indeterminate cytology; (b) a thyroid US image and (c) surgical resection with a histopathological result matching with the nodule’s location and size analyzed on US-Fine-needle aspiration cytology (FNAC)
Summary
Indeterminate thyroid nodules currently present a challenge for clinical decision-making. Thyroid nodules (TNs) are very common in clinical practice, with a prevalence of up to 68% by US in the general population [1]. Fine-needle aspiration cytology (FNAC) is an accurate and cost-effective tool in which benign and malignant diagnoses carry malignancy risks of approximately < 5 and > 96%, respectively [3]. The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) classifies indeterminate cytological results into 3 of 6 categories: Bethesda III - Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance (AUS/ FLUS), Bethesda IV - Follicular Neoplasm/Suspicious for a Follicular Neoplasm (FN/SFN) and Bethesda V - Suspicious for Malignancy (SM) [5]. The significant cost of the molecular markers and their unavailability in all health-care centers make their use in clinical practice unfeasible
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