This tumor heterogeneity is particularly important in relation to parity because parity and early age at first full-term birth are associated with reduced risk for ER-positive (ER+) or and (ER + or PR+) breast tumors, but they do not seem to reduce, or they may even increase, lifetime risk for ER-negative (ER-), particularly triple-negative (ER - and PR - and HER2-) breast tumors [8,18-23]. Here, ESR1 is linked to neoplasm.