Thus, cancer-related pathways may be perturbed in normal epithelium10,14. A similar study by Graham et al. using expression microarrays found a distinct signature distinguishes the normal epithelium of breast cancer cases, including both estrogen receptor positive (ER+) and ER− cancers, from that of controls (reduction mammoplasty samples), and this profile can be discerned in prophylactic mastectomy (PM). Here, ESR1 is linked to breast cancer.