Correlating the Bethesda System for Reporting Thyroid Cytopathology with Histology and Extent of Surgery: A Review of 21,746 Patients from Four Endocrine Surgery Registries Across Two Continents

Background: The Bethesda system for cytopathology (TBSRTC) is a 6-tier diagnostic framework developed to standardize thyroid cytopathology reporting. The aim of this study was to determine the risk of malignancy (ROM) for each Bethesda category. Methods: Thyroidectomy-related data from 314 facilities in 22 countries were entered into the following outcome registries: CESQIP (North America), Eurocrine (Europe), SQRTPA (Sweden) and UKRETS (UK). Demographic, cytological, pathologic and extent of surgery data were mapped into one dataset and analyzed. Results: Out of 41,294 thyroidectomy patient entries from January 1, 2015, to June 30, 2017, 21,746 patients underwent both thyroid FNA and surgery. A comparison of cytology and surgical pathology data demonstrated a ROM for Bethesda categories 1 to 6 of 19.2%, 12.7%, 31.9%, 31.4%, 77.8% and 96.0%, respectively. Male patients had a higher rate of malignancy for every Bethesda category. Secondary analysis demonstrated a high ROM in male patients with Bethesda 3 category aged 31–35 years (52.1%, 95% confidence interval (CI) 37.9–66.2%), aged 36–40 years (55.9%, 95% CI 39.2–72.6%) and aged 41–45 years (46.9%, 95% CI 33–60.9%). Patients with Bethesda 5 and 6 scores were more likely to undergo total thyroidectomy (65.9% and 84.6%); for patients with Bethesda scores 2 and 3, a higher percentage of females underwent total thyroidectomy compared to males in spite of a higher ROM for males. Conclusions: These data demonstrate that Bethesda categories 1–4 are associated with a higher ROM compared to the first edition of TBSRTC, especially in male patients, and validate findings from the second edition of TBSRTC.