Worakit Kaewnopparat, MD¹, Adiluck Pisutpunya, MD¹, Wanwisa Himakhun, MD¹

Background: Whole slide imaging (WSI) is a digital technology developed as an adjunct to, or an alternative modality for, conventional light microscopy (CLM) in pathological diagnosis. However, validation remains essential before implementation, particularly for breast core needle biopsy (CNB), where diagnostic accuracy is critical for patient management.

Objective: To validate the diagnostic concordance, reproducibility, and efficiency of WSI in comparison to CLM for the interpretation of CNB, encompassing histological assessment and biomarker evaluation, specifically estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (HER2), and Ki-67.

Materials and Methods: Three observers retrospectively assessed 79 CNB cases and biomarker subgroups using CLM and WSI after a 2-week washout. Agreement among observers was evaluated using Cohen’s kappa. The analysis focused on concordance, major and minor discordance, and interpretation time.

Results: Intra-observer agreement demonstrated substantial to almost perfect levels for hematoxylin and eosin (H&E) (κ=0.85 to 0.92) and biomarkers; ER (κ=0.80 to 0.84), PR (κ=0.69 to 1.00), HER2 (κ=0.80 to 0.89), and Ki-67 (κ=0.86 to 0.89), with p<0.001. The concordance rate for H&E was between 81% to 87%, with major discordance occurring in only 1% to 2.5% of cases. Biomarker concordance reached 80% to 90%, with the majority of discordances being minor. WSI interpretation time was comparable to or faster than CLM for most IHC markers, driven by user experience.

Conclusion: WSI demonstrates accuracy, reproducibility, and efficiency in the diagnosis of breast CNB, in accordance with the College of American Pathologists (CAP) validation standards. It is a safe alternative to microscopy and can be used in regular pathology, even in resource-bound settings.

Received 9 December 2025 | Revised 2 February 2026 | Accepted 3 February 2026

DOI: 10.35755/jmedassocthai.2026.5.03887