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

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 20162019 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.