ESR1 and breast cancer: The co-expression of HRs in HER2+ BC is consistently associated with more favorable clinicopathologic features than HR−/HER2+ BC, such as a lower stage based on the American Joint Committee on Cancer at diagnosis, lower histologic grade, and—in the case of triple-positive BC (estrogen receptor (ER+), progesterone receptor (PgR+), and HER2+ BC)—smaller median tumor size [12].