ESR1 and breast cancer: In our analyses, to obtain much more detailed information concerning the clinical implications of TIICs in breast cancer patients by analyzing ER- and HER2-predominant subtypes, a total of 2976 nonmetastatic breast tumor samples were classified into nine subtypes based on receptor status, including ER+PR+, ER+PR-, ER-PR+, ER-PR-, ER+HER2+, ER+HER2-, ER-HER2+, ER-HER2-, and ER-PR-HER2-.