Novel bright field molecular morphology methods for detection of HER2 gene amplification

Profiling the amplification and over-expression of the HER2 gene is a key component for defining the prognosis and management of invasive breast carcinoma. Clinical laboratory testing for HER2 gene amplification and over expression has been complicated by an unacceptably high rate of false positive immunohistochemistry (IHC) results, poor reproducibility for the '2+' category of IHC scoring, and reluctant acceptance of alternative testing by fluorescence in situ hybridization (FISH) by the diagnostic pathology community. Novel chromogenic in situ hybridization (CISH) assays have been developed that utilize bright field microscopy and a conventional light microscope for interpretation, but the analytical sensitivity of first generation CISH systems has been problematic. Novel second generation in situ hybridization detection methods based upon polymerized lg detection chemistry, autometallography or enzyme metallography, have been developed that routinely detect endogenous HER2 signals in normal cells (on slide hybridization control) and HER2 signals in both non-amplified and amplified patterns of HER2 genomic signatures. By combining the strength of polymerized peroxidase-labeled antibodies and metallography for gene amplification, with the detection of expression of HER2 encoded protein by IHC on the same slide, both HER2 gene amplification and protein over-expression can be simultaneously evaluated on a cell-by-cell basis in each microscopic field of carcinoma.