Alterations in estrogen signaling pathways in ERα+ breast tumors can arise from increased growth factor signaling, such as epidermal growth factor receptor (EGFR) and AKT/mammalian target of rapamycin (mTOR) pathways, and more recently to ERα isoform variation [2,4,5,6,7,8]. Here, ESR1 is linked to breast neoplasm.