CAF1, CAF2, and CAF3 were randomly selected from a series of consecutively collected breast cancer biopsies, which by immunohistochemical staining for GATA3, ER, progesterone receptor (PR), cytokeratin 5 (K5), cytokeratin 14 (K14) and human epidermal growth factor receptor 2 (HER2) were classified as ER+ luminal breast carcinomas (Table 1). Here, ESR1 is linked to breast cancer.