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.