Cytologic atypia is predictive of increased risk of malignancy and BRAF mutations in thyroid follicular neoplasms (Bethesda category IV).

INTRODUCTION

Molecular testing on thyroid fine needle aspirations with indeterminate cytology is integral to patient management. The aim of this study was to investigate the risk of malignancy in nodules diagnosed as Bethesda category IV, follicular neoplasm (FN), with and without cytologic atypia.

MATERIALS AND

METHODS

A total of 186 thyroid fine needle aspirations classified as Bethesda category IV (FN) were identified, and were categorized as FN with cytologic atypia or without cytologic atypia. Of those, 162 (88%) of cases had associated molecular testing. Cases diagnosed as oncocytic follicular neoplasm were excluded.

RESULTS

The risk of malignancy for category IV FN with cytologic atypia was 66.7% and without cytologic atypia was 36.8%. FN with cytologic atypia harbored more BRAF-like alterations (BRAF_V600E, RET, ETV6/NTRK3) than those without.

CONCLUSIONS

Subdividing FN based on cytologic atypia might better risk stratify lesions and guide patient management.