Validation of the Bethesda System for Reporting Thyroid Cytopathology in a Danish tertiary centre.

ABSTRACT

INTRODUCTION: The Bethesda System for Reporting Thyroid Cytopathology (BSRTC) is used to categorise thyroid fine-needle aspiration (FNA). The aim of this study was to validate the BSRTC in a consecutive cohort and to evaluate the derived management in terms of performing repeat FNA or thyroid surgery. METHODS: Results of thyroid FNAs assessed at the Department of Pathology, Aarhus University Hospital, in the period 2016-2019 were retrieved from The Danish Pathology Registry. FNA category according to the BSRTC along with the histological diagnosis (if available) were linked to the individual patient. RESULTS: In total, 3,669 biopsies were included from 2,873 thyroid nodules in 2,547 patients. Repeat FNA was performed in 23.6% of nodules. The majority of primary FNAs were Benign (BSRTC II; 52.4%). Non-diagnostic (ND) (BSRTC I) was found in 26.3% and BSRTC III-VI were found in 3.6-7.5%. Compared with the first with the last FNA, the frequency of Benign (BSRTC II) increased (61.3%), whereas the frequency of ND (BSRTC I) decreased (14.8%). Surgery was performed in 38.2% (n = 1,097) of nodules. The malignancy rate of 11.5% correlated positively with the BSRTC category, being 2.8% in Benign (BSRTC II) and 95.7% in Malignant (BSRTC VI). CONCLUSIONS: The malignancy rates in the BSRTC categories were in accordance with reports from other countries. Since the BSRTC ensures a standardised and concise communication of cytopathology assessments, application of the BSRTC for thyroid nodule management in a Danish setting is recommended. FUNDING: None. TRIAL REGISTRATION Not relevant.