Thyroid Research and Practice

: 2018  |  Volume : 15  |  Issue : 1  |  Page : 1--2

The Bethesda system for reporting thyroid cytopathology: A relook

Kaushik Pandit1, Ipsita Ghosh2,  
1 Department of Endocrinology, Belle Vue Clinic, Kolkata, West Bengal, India
2 Department of Endocrinology, IPGME&R, Kolkata, West Bengal, India

Correspondence Address:
Dr. Kaushik Pandit
Belle Vue Clinic, Kolkata, West Bengal

How to cite this article:
Pandit K, Ghosh I. The Bethesda system for reporting thyroid cytopathology: A relook.Thyroid Res Pract 2018;15:1-2

How to cite this URL:
Pandit K, Ghosh I. The Bethesda system for reporting thyroid cytopathology: A relook. Thyroid Res Pract [serial online] 2018 [cited 2023 Feb 1 ];15:1-2
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Fine-needle aspiration (FNA) has established itself as a cost-effective and essential tool in the evaluation of euthyroid patients with thyroid nodules. It is also critical that cytopathologists communicate the report of thyroid FNA to the referring physicians in terms that are unambiguous, succinct, and clinically meaningful. Historically speaking, there have been many efforts to standardize the terminology of thyroid FNA, namely British Association–Royal College of Physicians in 2004,[1] followed by the modification proposed by Italian Society of Pathology and Cytopathology–Italian Section of the International Academy of Pathology in 2007.[2] Moreover, it was in the year 2009 the publication of the National Cancer Institute (NCI), Bethesda, USA, which proposed a 6-class FNA reporting system that was widely accepted worldwide for its simplicity, reproducibility, and unambiguousness and ultimately improved clinical significance, usefulness, and predictive value of thyroid FNA, “The Bethesda System for Reporting Thyroid Cytopathology” (TBSRTC).[3] Bethesda system, like all classification systems, provides a category for nondiagnostic FNA samples, a category for benign lesions, and a category for malignant lesions. However, there are also some remarkable differences. The Bethesda system introduced two categories for borderline lesions: “atypia/follicular lesion of undetermined significance” (AUS/FLUS) and “follicular neoplasm or suspicious for a FN” (FN/SFN). In contrast, the British and the Italian reporting systems provided a single category for all borderline lesions, named follicular lesion and follicular proliferation, respectively. In addition, the British and the Italian systems preferred providing a numeric coding for each category. However, initially, this novel introduction of two categories for the borderline lesions raised many concerns such as, are these criteria adequate to ensure satisfactory interobserver and intraobserver diagnostic reproducibility? Are they uniformly applicable? Is variations expected out of FNA procedure itself? Do these criteria, by themselves, provide sufficient information to decide the management of patients with nodular thyroid lesions? Hopefully, the widespread acceptability of the Bethesda system has provided sufficient proof of confidence of the cytologist community in its scientific rigor in providing triage for the treatment of nodular thyroid disease.

The British Thyroid Association together with the Royal College of Pathologists along with the Italian Society of Pathology embraced the NCI philosophy on publication of the TBSRTC to devise a 6-tiered scheme by subclassifying the FNs into the two subgroups of Thy3a (atypia), corresponding to the Bethesda AUS/FLUS, and Thy3f (FN), corresponding to the FN/SFN of the NCI Conference, leading to a good diagnostic agreement among cytopathologists.[4] It should be noted that, in the British system, all cases categorized either as indeterminate or suspicious should be referred to the multidisciplinary team to establish a correct management. In contrast, the Japan Thyroid Association has published in English its national guidelines wherein it includes a suggestion for reporting the cytology of thyroid nodules from a minimum of six to a maximum of eight categories, depending on whether or not the cytopathologist chooses to subdivide the FN/indeterminate group.[5]

Recently, the NCI, in 2017, has published a revision and update on the reporting for thyroid cytology based on the symposium entitled ''The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC): Past, Present, and Future'' held at the October 2016 International Congress of Cytology in Yokohama, Japan. The 2017 revision was inspired by new data and new developments in the field of thyroid pathology: revised guidelines for the management of patients with thyroid nodules, the introduction of molecular testing as an adjunct to cytopathologic examination, and the reclassification of the noninvasive follicular variant of papillary thyroid carcinoma as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP).[6]

The other important changes incorporated in the 2017 update are (i) the risks of malignancy have been recalculated based on the updated available data. (ii) The risks of malignancy are shown two ways: first, when NIFTP is not considered a malignancy, and second, when NIFTP is still included among the “carcinomas.” The higher risk estimates may have more clinical relevance because they are defined for surgical disease. (iii) The categories AUS/FLUS and FN/SFN now have the option of molecular testing. (iv) The definition and diagnostic criteria for FN/SFN have been revised in light of the new entity of NIFTP. (v) The definition and diagnostic criteria for the papillary thyroid carcinoma subset of the malignant category have been modified to limited use for “classical” features of papillary thyroid carcinoma. (vi) Optional education notes may be used for the subsets of FN/SFN and suspicious for malignancy with cytomorphologic features suggestive of follicular variant of papillary thyroid carcinoma or NIFTP. (vii) An optional education note may be used for “malignant; papillary thyroid carcinoma” cases to acknowledge that a small proportion may prove to be NIFTP.

We believe that despite the new 2017 TBSRTC is closely aligned with the original 2009 TBSRTC, the changes are substantial reflecting the growing knowledge based on the subject, especially because of the developments due to access and application of new technology in this realm.


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