A key finding is that a five-biomarker panel consisting of estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor 2 (Her2), CK5/6, and epidermal growth factor receptor (EGFR) shows promise in categorizing invasive breast cancers into their corresponding molecular subtypes (Cheang et al.). This evidence concerns the gene PGR and invasive breast carcinoma.