Analysis of the Bethesda System for Reporting Thyroid Cytopathology and Similar Precursor Thyroid Cytopathology Reporting Schemes

Abstract

The Bethesda System for Reporting Thyroid Cytopathology is a standardized reporting system for classifying thyroid fine-needle aspiration results comprising of 6 diagnostic categories with unique risks of malignancy and recommendations for clinical management. The majority of thyroid nodules are benign; however, up to 30% of fine-needle aspiration of thyroid nodule results are equivocal. Until 2007, various diagnostic terms were used to classify such cases, including "atypical," "indeterminate," and rule-out or cannot exclude malignancy. A literature review of 13 original studies was conducted to evaluate whether utilization of the Bethesda System for Reporting Thyroid Cytopathology nomenclature represent an improvement over thyroid cytopathology reporting schemes used before 2007 in diagnosing thyroid malignancy. The sensitivity and specificity of thyroid fine-needle aspiration was high in the studies that assessed the measures. However, a selection bias exists and most studies do not include indeterminate diagnosis in their calculations. Although the Bethesda System for Reporting Thyroid Cytopathology recommends a repeat fine-needle aspiration to follow-up nondiagnostic specimens, in the majority of studies, an appreciable number of cases underwent follow-up surgical biopsy or thyroidectomy. The diagnostic category of atypia/follicular lesion of undetermined significance remains heterogenous in terms of usage and clinical outcome. The majority of the studies that utilize the Bethesda System for Reporting Thyroid Cytopathology in this literature review retrospectively reclassified thyroid fine-needle aspiration into the Bethesda System for Reporting Thyroid Cytopathology nomenclature with reported malignancy rates that are similar between cases reclassified as atypia/follicular lesion of undetermined significance and follicular neoplasm/suspicious for follicular neoplasm.

Diagnosis of atypia/follicular lesion of undetermined significance: An institutional experience

“…[3] In the study by Jo et al ., a majority of initial AUS/FLUS cases received follow-up surgery rather than the recommended repeat FNA. [4] Renshaw, in concordance with other studies, noted that thyroid FNA cases subcategorized as AUS/FLUS – not otherwise specified and AUS/FLUS - rule out follicular neoplasm had a similar malignancy rate to cases diagnosed as follicular neoplasm (FN)/suspicious for follicular neoplasm (SFN).…”

Terminology and nomenclature schemes for reporting thyroid cytopathology: An overview

“…11,16,37 This diagnostic approach lends itself to risk-based clinical management algorithms. 11,16,17,37 In contrast, although the Thy and TIR systems appear to be predicated on the idea that the increasing diagnostic categorical number correlates with increasing risk of malignancy, the design was not data driven or risk based from the outset. 38 This is exemplified in that both terminologies provide malignancy risks derived primarily from data utilized in the development of TBSRTC, as well as studies that used previous diagnostic categories and in some cases "clinical experience" without data.…”

“…Thus, for the first time, in a non-gynecologic setting, a multidisciplinary approach formulated a definitive, finite group of diagnostic categories that could be correlated with a clinical management plan. 11,16,17 In contrast, the UK did have a terminology in existence since 2002, proposed initially by the British Thyroid Association (BTA) and Royal College of Physicians (RCP). 18 This terminology, commonly referred to as the Thy categories (Thy1-5), was recommended along with a descriptive diagnosis and released within their published guidelines.…”

“…22,23 The criteria for the diagnostic categorization for TBSRTC was constructed on the basis that each discrete category had an associated positive predictive value for malignancy. 17 The intent of this design was to create a clinical management algorithm that would correlate with these diagnostic categories. 17 Although the BTA/RCP terminology system was the first of its kind, it was really designed initially as an adjunct to a descriptive diagnosis with only a suggested clinical action.…”

“…17 The intent of this design was to create a clinical management algorithm that would correlate with these diagnostic categories. 17 Although the BTA/RCP terminology system was the first of its kind, it was really designed initially as an adjunct to a descriptive diagnosis with only a suggested clinical action. The diagnostic categories were not based on predictive values of malignancy but rather modeled from other cytology reporting schemes, i.e., breast (C1-5; NHS breast screening program) with the view of mapping these five-tiered categories to the TBSRTC categories.…”