Atypia of undetermined significance/follicular lesion of undetermined significance (Bethesda Category - III) in thyroid cytology: Experience from a tertiary health care center from Eastern India

Abstract

Introduction: Fine-needle aspiration (FNA) cytology is a reliable method to diagnose thyroid lesions. The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) is universally followed for thyroid cytology reporting. Out of the six categories described, Category III, atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) is the most heterogeneous one. Materials and Methods: In this study conducted in a tertiary health care center in Eastern India over 2 ½-year period, 868 thyroid FNAs were performed and the cytology smears were interpreted using the TBSRTC. There were 32 FNAs in Category III. Histopathology report was available in nine cases. Results: The risk of malignancy (ROM) considering noninvasive follicular thyroid carcinoma with papillary nuclear features (NIFTP) as benign was 9.3% and by considering NIFTP as malignant was 21.8%. Conclusion: The ROM for AUS/FLUS in our study was within the revised ROM criteria. In Category III, surgery is preferable in nodules which harbor suspicious features either clinically or according to ultrasound findings.