Malignancy Risk for Fine-needle Aspiration of Thyroid Lesions according to the Bethesda System for Reporting Thyroid Cytopathology

Vickie Y. Jo, MD; Edward B. Stelow, MD; Simone M. Dustin, MD; Krisztina Z. Hanley, MD

Disclosures

Am J Clin Pathol. 2010;134(3):450-456. 

In This Article

Abstract and Introduction

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.

Introduction

Fine-needle aspiration (FNA) of the thyroid gland has proven to be an important and widely accepted, cost-effective, simple, safe, and accurate method for triaging patients with thyroid nodules.[1] It is estimated that up to 30 million patients in the United States have thyroid nodules larger than 1 cm. In comparison with the high prevalence of thyroid nodules, 30,000 patients are diagnosed with thyroid malignances each year.[2,3] FNAs provide information that guides the management of patients with thyroid nodules by identifying patients who require surgical resection and patients who require no further interventions.

Thyroid cytopathology practice requires communication and collaboration among pathologists and primary clinicians, endocrinologists, radiologists, and surgeons, as well as correlation with surgical pathology interpretations.[4] Therefore, consistent diagnostic terminology is imperative. While there are minimal difficulties in diagnosing most benign and overtly malignant lesions, diagnostic challenges arise when aspirate samples are quantitatively or qualitatively suboptimal to reliably exclude a neoplastic process. The management of these types of lesions has been further complicated by the historic lack of universal terminology.[5] Multiple organizations have proposed diagnostic guidelines for reporting thyroid FNA cytology results, including the Papanicolaou Society of Cytopathology Task Force[6] and the American Thyroid Association,[7] although none have been necessarily universally accepted.

Throughout 2007, the National Cancer Institute (NCI) organized The NCI Thyroid Fine Needle Aspiration State-of-the-Science Conference. The current status of various aspects of thyroid FNA was discussed, including the following: (1) indications and pre-FNA requirements, (2) training and credentialing for FNA, (3) technique, (4) reporting terminology and morphologic criteria, (5) ancillary studies, and (6) post-FNA testing and treatment.[8] Since the conference, there has been an initiative to publish an atlas and guidelines using a standardized nomenclature for the interpretation of thyroid FNAs, known as The Bethesda System for Reporting Thyroid Cytopathology.[9–11] The atlas describes 6 diagnostic categories of lesions: nondiagnostic or unsatisfactory, benign, atypia of undetermined significance/follicular lesion of undetermined significance, follicular neoplasm/"suspicious" for follicular neoplasm, suspicious for malignancy, and malignant Table 1.

The 6 diagnostic categories of the forthcoming Bethesda System have individual implied risks of malignancy that influence management paradigms Table 2, reflecting literature reviews and institutional studies.[9,12–14] Herein, we review the experience at the University of Virginia Health System, Charlottesville, with thyroid FNA modified to reflect this new reporting system and compare it with previous large-scale studies.

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