This is important for two reasons: first, pathologic complete response to neoadjuvant chemotherapy, defined as the complete absence of invasive tumor cells in the breast and lymph nodes after treatment, occurs almost exclusively in tumors negative for ER [12-15]; second, ER-negative tumors typically feature higher levels of TIL than do ER-positive tumors [6,11,16-18]. Here, ESR1 is linked to neoplasm.