Analysis of the gene expression profiles and the immunohistochemical expression of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2), has been used to divide breast carcinomas into five intrinsic subtypes: luminal A, luminal B, HER2-enriched, basal and claudin-low [4]. Here, ESR1 is linked to breast carcinoma.