Communication
The 2017 Bethesda System for Reporting Thyroid Cytopathology

https://doi.org/10.1016/j.jasc.2017.09.002Get rights and content

The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) established a standardized, category-based reporting system for thyroid fine-needle aspiration (FNA) specimens. The 2017 revision reaffirms that every thyroid FNA report should begin with 1 of 6 diagnostic categories, the names of which remain unchanged since they were first introduced: (1) Nondiagnostic or Unsatisfactory; (2) Benign; (3) Atypia of Undetermined Significance (AUS) or Follicular Lesion of Undetermined Significance (FLUS); (4) Follicular Neoplasm or Suspicious for a Follicular Neoplasm; (5) Suspicious for Malignancy; and (6) Malignant. There is a choice of two different names for some of the categories: a laboratory should choose the one it prefers and use it exclusively for that category; synonymous terms (eg, AUS and FLUS) should not be used to denote 2 distinct interpretations. Each category has an implied cancer risk that ranges from 0% to 3% for the “Benign” category to virtually 100% for the “Malignant” category, and, in the 2017 revision, the malignancy risks have been updated based on new (post 2010) data. As a function of their risk associations, each category is linked to updated, evidence-based clinical management recommendations. The recent reclassification of some thyroid neoplasms as non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) has implications for the risk of malignancy, and this is accounted for with regard to diagnostic criteria and optional notes. Such notes can be useful in helping guide surgical management.

Introduction

With its inception, The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) established a standardized reporting system with a limited number of diagnostic categories for thyroid fine-needle aspiration (FNA) specimens. Using TBSRTC, cytopathologists can communicate their interpretations to the referring physician in terms that are succinct, unambiguous, and clinically useful.1, 2, 3

TBSRTC has been widely adopted in the United States and in many places worldwide and has been endorsed by the American Thyroid Association.4 It has improved communication and provided a uniform template for sharing data among investigators. Since its acceptance in clinical practice, however, questions have arisen over the proper use of the diagnostic categories, the associated risks of malignancy, and the appropriate management. By 2016 the time had come to consider revisions. The 2017 revision described herein was inspired by new data and new developments in the field of thyroid pathology: revised guidelines for the management of patients with thyroid nodules,4 the introduction of molecular testing as an adjunct to cytopathologic examination, and the reclassification of the non-invasive follicular variant of papillary thyroid carcinoma as non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP).5 Much of the groundwork for this revision was laid down by a symposium entitled “The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC): Past, Present, and Future” at the 2016 International Congress of Cytology in Yokohama, Japan. Preparations for the symposium began 12 months earlier with the designation of a steering group and the appointment of an international panel of 16 cytopathologists and an endocrinologist whose task was to review and summarize the published literature in English since the introduction of TBSRTC.

The symposium, moderated by Drs. Syed Ali and Philippe Vielh, took place on May 30, 2016, and the discussions and recommendations from the symposium have been summarized in a publication by Pusztaszeri et al.6 Based on the panel's recommendation, the 6 original general categories (“Nondiagnostic/Unsatisfactory [ND/UNS],” “Benign,” “Atypia of Undetermined Significance/Follicular Lesion of Undetermined Significance [AUS/FLUS],” “Follicular Neoplasm/Suspicious for a Follicular Neoplasm [FN/SFN],” “Suspicious for Malignancy [SUS],” and “Malignant”) have been retained in the 2017 revision, and a revised atlas is in press, with updated and expanded chapters devoted to these categories and refined definitions, morphologic criteria, and explanatory notes.7

Section snippets

Format of the report

For clarity of communication, the 2017 BSRTC continues to recommend that each report begin with a general diagnostic category. Because they are more ambiguous and less clearly descriptive, numerical designations alone (eg, “Bethesda III”) are discouraged for the purposes of cytologic reporting, although the numerical designations may be used in conjunction with the category name—for example, “Atypia of Undetermined Signficance (Bethesda III).”

The 6 general diagnostic categories are unchanged

Highlights of the 2017 Bethesda System for Thyroid Cytopathology

The original 6 categories remain unchanged, but a number of enhancements have been introduced with the 2017 BSRTC:

  • 1.

    The risks of malignancy have been recalculated based on post-2010 data.

  • 2.

    The risks of malignancy are shown two ways (see Table 2): (1) when NIFTP is not considered a malignancy; and (2) when NIFTP is still included among the “carcinomas.” The higher risk estimates may have more clinical relevance because they are defined for surgical disease.

  • 3.

    The “usual management” of AUS/FLUS and

Acknowledgments

The authors thank Dr. Erik Alexander for his review of the manuscript and helpful comments.

References (23)

  • M.E. Iskandar et al.

    Evidence for overestimation of the prevalence of malignancy in indeterminate thyroid nodules classified as Bethesda category III

    Surgery

    (2015)
  • R.T. Schlinkert et al.

    Factors that predict malignant thyroid lesions when fine-needle aspiration is “suspicious for follicular neoplasm”

    Mayo Clinic Proc

    (1997)
  • E.S. Cibas et al.

    The Bethesda System for Reporting Thyroid Cytopathology

    Thyroid

    (2009)
  • E.S. Cibas et al.

    The Bethesda System For Reporting Thyroid Cytopathology

    Am J Clin Pathol

    (2009)
  • S.Z. Ali et al.

    The Bethesda System for Reporting Thyroid Cytopathology: Definitions, Criteria and Explanatory Notes

    (2009)
  • B.R. Haugen et al.

    2015 American Thyroid Association management guidelines for adult patients with thyroid nodules and differentiated thyroid cancer: The American Thyroid Association Guidelines Task Force on Thyroid Nodules and Differentiated Thyroid Cancer

    Thyroid

    (2016)
  • Y.E. Nikiforov et al.

    Nomenclature revision for encapsulated follicular variant of papillary thyroid carcinoma: a paradigm shift to reduce overtreatment of indolent tumors

    JAMA Oncol

    (2016)
  • M. Pusztaszeri et al.

    The Bethesda System for Reporting Thyroid Cytopathology: proposed modifications and updates for the second edition from an international panel

    Acta Cytol

    (2016)
  • S. Ali et al.

    The Bethesda System for Reporting Thyroid Cytopathology: Definitions, Criteria, and Explanatory Notes

    (2018)
  • A.A. Renshaw

    Histologic follow-up of nondiagnostic thyroid fine needle aspirations: implications for adequacy criteria

    Diagn Cytopathol

    (2012)
  • M. Vivero et al.

    Adequacy criteria for thyroid FNA evaluated by ThinPrep slides only

    Cancer

    (2017)
  • Cited by (98)

    • The 2023 Bethesda System for reporting thyroid cytopathology

      2023, Journal of the American Society of Cytopathology
    • A Triumvirate:: Correlating Thyroid Cytopathology, Molecular Testing, and Histopathology

      2023, Surgical Pathology Clinics
      Citation Excerpt :

      Aspirates composed of follicular cells with an altered architectural pattern characterized by significant crowding and/or predominance of microfollicles are classified as SFN.1 The estimated ROM for the SFN category ranges from 25% to 40%.1 Management of patients with indeterminate cytology can be challenging.

    View all citing articles on Scopus

    This article is being published jointly in Thyroid and Journal of the American Society of Cytopathology.

    View full text