Human Epidermal Growth Factor Receptor 2-Low Breast Cancer: Prevalence Rate and Scoring Concordance Among...

Area of Science:

• Oncology
• Pathology
• Genetics

Background:

• Emerging anti-HER2 therapies benefit breast cancer with low human epidermal growth factor receptor 2 (HER2) expression.
• This study investigates the prevalence of HER2-low breast cancer and pathologist scoring concordance in Jordan.

Purpose of the Study:

• To determine the prevalence of HER2-low breast cancer.
• To evaluate interpathologist concordance in HER2 scoring using 2018 ASCO/CAP guidelines.

Main Methods:

• Retrospective observational study of 116 breast cancer samples.
• Independent HER2 scoring by 3 pathologists using 2018 ASCO/CAP guidelines.
• Concordance analysis using Fleiss' kappa and Cohen's weighted kappa statistics.

Main Results:

• HER2-low tumors (1+ or 2+ IHC with negative FISH) comprised 72.4% of cases.
• Substantial interpathologist agreement was observed (Cohen's kappa 0.691-0.849, Fleiss' kappa 0.645).
• Complete agreement among pathologists occurred in 67.2% of cases.

Conclusions:

• HER2-low breast cancer is highly prevalent in the Jordanian population.
• Substantial interpathologist agreement in HER2 scoring supports reliable clinical application.
• Findings emphasize the importance of standardized HER2 assessment for targeted therapy in Jordan.