ESR1 and breast cancer: We used a panel of 15 well-established clinical markers (Table 1), including estrogen receptor (ER) and progesterone receptor (PR), the proliferation associated protein Ki67, adherens junctions (E-cadherin, β-catenin, P-cadherin, and p120-catenin), the luminal differentiation marker GATA-3, the transcription factor TFAP2-beta, the luminal cytokeratins CK8/18 and CK7, the HER2 that drives 10% of breast cancer cases, the tumor suppressor p53, the cytokeratins CK5/14, and the myoepithelial marker p63.