Dauphine et al. analyzed 826,599 female patients enrolled in the National Cancer Database (2004–2015), finding that single HR-positive BC subtypes (ER+/PgR- and ER-/PgR+) are more likely to have high-grade cancer, lymphovascular invasion, node-positive cancer, stage 4 cancer, a higher multigene assay score, and a worse prognosis than the ER+/PgR+ subtype [31]. This evidence concerns the gene ESR1 and cancer.