Ultrasound-Guided Fine-Needle Aspiration or Core Needle Biopsy for Diagnosing Follicular Thyroid Carcinoma?

Ko Woon Park; Jung Hee Shin; Soo Yeon Hahn; Young Lyun Oh; Sun Wook Kim; Tae Hyuk Kim; Jae Hoon Chung

Disclosures

Clin Endocrinol. 2020;92(5):468-474. 

In This Article

Abstract and Introduction

Abstract

Objective: We evaluated the preoperative diagnostic values of ultrasound (US), fine-needle aspiration (FNA) and core needle biopsy (CNB) leading to surgery in patients with FTC.

Methods: From October 1994 to July 2016, 298 patients with FTC who had preoperative US images and underwent US-guided FNA or CNB and surgery were included in this study. We evaluated the results of preoperative FNA or CNB based on the Bethesda system and the US findings according to the Korean thyroid imaging reporting and data system (K-TIRADS).

Results: Predominant US features of FTC showed solid, hypo- or so-echogenicity, oval smooth margin and halo with no calcification. Based on K-TIRADS, 140 (47.0%) patients with FTC were categorized as low suspicion, 133 (44.63%) as intermediate suspicion and 25 (8.4%) as high suspicion at US. Considering only FNA cytology (n = 230), 6.9% were revealed as Bethesda class I, 16.1% as class II, 37.0% as class III, 29.1% as class IV and 10.9% as class V. Considering the 68 cases with CNB results, 2.9% were revealed as class I, 4.4% as class II, 20.6% as class III and 72.1% as class IV. Despite multiple FNAs, 16.7% of the 84 patients with FTC still obtained Bethesda class I or class II. CNB results in patients with FTC had a significantly higher rate of Bethesda class IV compared to the FNA results (P < .001). FTCs with distant metastasis exhibited a significantly higher rate of Bethesda classes IV and V compared to those without distant metastasis (P = .004).

Conclusion: Surgery for FTC is deferred only with preoperative US and FNA. CNB in patients with FTC can lead to surgery better than FNA. Therefore, if the US feature is characteristic and a serially growing large nodule is suspected, the first attempt of CNB may be helpful in selecting a surgical candidate.

Introduction

Follicular thyroid carcinoma (FTC) is the second most common type of thyroid cancer after papillary thyroid carcinoma, consisting of 10%-15% of cases of all thyroid cancers.[1–3] Ultrasound (US)-guided fine-needle aspiration (FNA) has been established as the gold standard for diagnosis of thyroid malignancies, and the Bethesda System for Reporting Thyroid Cytopathology (BSRTC) stratifies the malignancy risk based on FNA results,[4] which can help with decision-making regarding management of thyroid nodules. The malignancy risk of thyroid nodules depends on US features, and it may differ according to features such as nondiagnostic,[5] benign[6–9] and indeterminate[10–15] FNA results. Recently, the Korean Society of Thyroid Radiology suggested a US malignancy risk-stratification system for thyroid nodules, the Korean Thyroid Imaging Reporting and Data System (K-TIRADS), where the malignancy risk is stratified by US patterns in terms of integrated solidity, echogenicity and suspicious US features.[16] However, even though US features are the basis, FNA possesses a weakness when differentiating follicular thyroid carcinomas (FTCs) from follicular adenomas (FAs) or adenomatoid nodules because the diagnosis of FTC and FA can be established only based on histologic evidence of resected specimens such as capsular invasion and vascular invasion. US-guided core needle biopsies (CNB) are safe and well-tolerated, producing a larger tissue sample that can facilitate a more precise histologic diagnosis, while modified core biopsy techniques have improved the diagnostic performance of circumscribed solid thyroid nodules and can result in selection of proper surgical candidates.[17]

So far, known suspicious US findings for cancer prediction are related to papillary thyroid carcinoma (PTC), and there are few reports about risk stratification for FTC. In this study, we evaluated the preoperative diagnostic values of US, fine-needle aspiration (FNA) and core needle biopsy (CNB) to perform surgery in patients with FTCs.

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