The HERmark assay uses a dual-antibody, proximity-based immunoassay approach, the VeraTagTM technology (Monogram Biosciences), to make precise and quantitative measurement of total HER2 protein expression (H2T) with greater sensitivity and specificity than immunohistochemistry (IHC), and provides a continuum of H2T values over approximately a 1,000-fold dynamic range in human breast cancers and cell lines [15]. The gene discussed is ERBB2; the disease is breast cancer.