Evaluating Low HER2 Status in Invasive Breast Carcinoma via HER2 Immunohistochemistry, with HER2 FISH Correlation: A Cohort of 112 Patients.

Our data support the need for finer granularity, classification, and understanding of HER2-low breast cancers. We also show that reproducibility between trained BP can be obtained, albeit with scoring at high power and low threshold for showing challenging interpretations.