Utility of whole‐slide imaging for rapid evaluation of thyroid FNA: A multireader prospective study

Background Rapid on‐site evaluation (ROSE) of thyroid fine‐needle aspiration biopsy (FNAB) improves diagnostic adequacy and facilitates ancillary molecular testing. In this prospective, multireader study, the authors evaluated the feasibility of using whole‐slide images (WSIs) for ROSE to determine specimen adequacy and preliminary categorization (according to The Bethesda System for Reporting Thyroid Cytopathology [Bethesda]) of image‐guided thyroid FNABs compared with conventional light‐microscopic (LM) examination of the same specimens in a referral cancer center. Methods The authors evaluated 98 ultrasound‐guided thyroid FNAB cases. Smears were stained with Papanicolaou and Diff‐Quik and were scanned at ×20 magnification using a Leica Aperio CS2 scanner. Five cytopathologists evaluated specimen adequacy and Bethesda categorization using WSI followed by LM assessment after a 2‐week washout. Intraobserver and interobserver agreements were calculated using Cohen and Fleiss kappa (κ) statistics. Scan time, interpretation time, and the need for ×40 magnification or z stacking were recorded. Results In total, 463 slides were scanned, with mean scan time of 5.48 minutes. WSI quality was acceptable in most cases. Z stacking and ×40 magnification were requested in 23% and 14% of reviews, respectively. Intrareader agreement between WSI and LM examination was excellent (κ = 0.86–0.95). Inter‐reader agreement was moderate for both WSI (κ = 0.48) and LM examination (κ = 0.56). Concordance was highest for Bethesda categories I and VI and lowest for categories III–V. Interpretation with WSI took significantly longer than with LM examination ( p < .0001). Conclusions WSI is a feasible alternative to LM examination for ROSE of thyroid FNABs, with high intrareader agreement and comparable inter‐reader agreement. The limited need for high magnification and z stacking supports its practical utility.