The Impact of Change in Practicing Cytopathologists' Team on Risk of Malignancy in a Retrospective Single‐Centre Project of 652 Thyroid Nodules: A Quality Assurance Project

INTRODUCTION: Fine needle aspiration cytology (FNAC) is a reliable, cost-effective method for evaluating thyroid lesions. The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) is a standardised framework for reporting FNAC interpretations, with each category implying a risk of malignancy (ROM) and recommending evidence-based clinical management. This project aimed to (i) determine ROM rates for thyroid FNAC in a 2-year period and (ii) investigate whether a personnel change in our cytology team influenced ROM rates. METHODS: We conducted retrospective research using a pathology database for FNAC of thyroid lesions between March 2022 and February 2024. Cytohistological correlation was made in cases with histopathological follow-up and ROM was calculated for each TBSRTC category. RESULTS: In a 2-year period, 652 FNAC specimens obtained from 553 patients were assessed. 28.2% (184/652) of cases had histopathological follow-up. ROM rates for each TBSRTC category were 3.6% (I), 4.9% (II), 2.9% (III), 12.5% (IV), 86.7% (V) and 100.0% (VI). After a personnel change, the distribution of TBSRTC categories shifted from categories III and IV to category II and ROM rates increased in categories II to IV. The cytohistological correlation showed limitations of FNAC interpretation in the two discrepant category II cases due to tumour subtype (diffuse sclerosing papillary thyroid carcinoma) and a retrospective lack of specimen representativeness. CONCLUSIONS: ROM rates are largely consistent with published data. A personnel change in our team shifted category distribution and ROM rates, illustrating the influence of interobserver variability on diagnostic thresholds. These findings underscore the need for ongoing quality assurance.