Discordance between Immunohistochemistry and ERBB2 mRNA to Determine HER2 Low Status for Breast Cancer

Novel HER2-directed antibody-drug conjugates have demonstrated efficacy in HER2-low expressing breast cancers, which are currently defined as those with immunohistochemistry (IHC) scores of 1+ or 2+ with a negative in situ hybridization assay. However, current HER2 testing methods are designed to identify HER2-amplified tumors with high expression levels. The true definition of HER2-low expressing breast cancers remains controversial. Using quantitative molecular analysis of breast cancers based on RNA expression, the dynamic range of HER2 expression exceeds that detected by in situ IHC approaches.
Source: Journal of Molecular Diagnostics - Category: Pathology Authors: Tags: Regular article Source Type: research