ESR1 and breast carcinoma: In breast carcinomas, associations between the tumor immune microenvironment and ER status have been investigated; the number of tumor-infiltrating lymphocytes (including FoxP3+, CD8+ or CD20+ cells) is greater in ERα-negative tumors than in ERα-positive tumors [28–31] and lymphocyte infiltration contributes to better clinical outcomes in ERα-negative tumors than in ERα-positive tumors [32].