Based on expression of molecular markers, all BC can be classified into several molecular subtypes: basal-like (ER−, PR−, Her2−, K5/14+, EGFR+), Her2 enriched (ER−, Her2+), claudin low (ER−, claudin−, vimentin+, E-cadherin low, Zeb1+), luminal A (ER high, Her2 low), luminal B (ER low, Her2 low, proliferation high) and normal breast-like (adipose tissue gene signature). This evidence concerns the gene ESR1 and breast cancer.