ESR1 and breast cancer: There were 4382 cases (12.47%) of HER-2(+) breast cancer: 83 ER(-)/PR(+) cases (1.89%), 774 ER(+)/PR(-) cases (17.66%), 2255 ER(+)/PR(+) cases (51.46%), and 1270 ER(-)/PR(-) cases (28.98%) (see Table 3 for details).