Interobserver Variability in HER2 Breast Biomarker Reporting: Implications for Diagnostic Consistency and Treatment Precision
Keywords:
ASCO Guidelines, Equivocal Cases, Human Epidermal Growth Factor Receptor 2, Interobserver Variability, Invasive Breast Cancer.Abstract
Objective: To assess the interobserver variability in HER2 immunohistochemical stain interpretation by pathologists of different strata of experience.
Study Design: Cross-sectional observational study.
Place and Duration of Study: Chughtai Institute of Pathology at Lahore, during a three-month interval from 01/6/2024 to 31/8/2024.
Materials and Methods: Fifty cases (n=50) of invasive breast cancer were included by random probability sampling and blocks were retrieved through respective biopsy reports by the laboratory information system. All the cases of ductal carcinoma in situ (DCIS) and salivary gland-like tumors of the breast were excluded. HER2 antibody was applied to these cases and interpreted by four histopathologists with varying years of reporting experience. Interobserver variability was observed by using the Cohen's and Fleiss kappa tests. A p-value of ≤0.05 was considered statistically significant.
Results: All patients were female, with a mean age of 46.3 years ± 12.87. The highest concordance was observed at a score of 3, while the greatest discordance occurred at a score of 2, with kappa values of 0.81 and 0.35, respectively, and a p-value of <0.01.
Conclusion: The highest interobserver variability was observed in the assessment of HER2 score 2, highlighting the challenges in interpreting equivocal cases.
