ESR1 and breast cancer: The MammaPrint and BluePrint assays (Agendia) for quantifying the expression levels of 70 and 80 genes, respectively, in the early stage breast cancer for guiding chemotherapy, estimating the risk of recurrence [66] and for molecular classification of breast cancer [67] and the breast cancer index (BCI) PCR-based 7-gene prognostic assay, to predict response to Tamoxifen and clinical outcomes including distant recurrence in ER-positive cases [68,69].