Either ESR1-positive and/or ESR2-low pT1 tumors.Introduction Estrogens influence the aggressiveness of breast cancer through their cognate nuclear receptors. In particular, the estrogen receptor-alpha (ERa) (ESR1) - present in tumor cells of about 70 to 75 of all breast tumors is considered crucial because of its proliferationinducing actions and for that reason is an important target for therap