ESR1 and breast cancer: Genomic Health Inc. (GHI) in collaboration with National Surgical Adjuvant Breast and Bowel Project (NSABP) researchers have recently developed and commercialized a predictive gene signature-based assay for ER-positive, LN-negative tamoxifen-treated breast cancer tumours, named Oncotype DX [28], measuring the expression of 21 genes on archival FFPE pathology blocks.