ESR1 and cancer: In early HR+/HER2- cancer, which had relatively lower mutation incidence and immune infiltration, positive lymph node, ER%<10%, and combined positive score ≥1 were associated with higher pCR rate with neoadjuvant pembrolizumab treatment (3), and elevated PD-L1 scores, ER%<50%, PR%<10%, and stromal TILs ≥1% indicated pCR and no residual cancer burden with neoadjuvant nivolumab therapy (4).