ESR1 and breast cancer: In addition, breast cancer is a heterogeneous disease, with potentially distinct etiology for different hormone receptor statuses, and it has been suggested that estrogen receptor-positive breast tumors (ER+) are more strongly associated with hormone-related factors than estrogen receptor-negative tumors (ER-) (43); therefore, assessing risk factors for breast cancer incorporating molecular pathological information may confer even greater insights (44).