ESR1 and breast cancer: In our study, the variables significantly associated with the decision to administer adjuvant chemotherapy in pT1a-pT1b breast cancers were younger age and the biological markers associated with a poor prognosis (grading G3, high proliferative index, ER-negative status and HER2-positive status) [14,16,21-28], and also predictive of chemoresponsivity in the neoadjuvant setting.