ESR1 and breast carcinoma: Because standard six-marker IHC analysis, as used in this study, can subdivide ER– breast cancers into the distinct subtypes of HER2+/ER–, core basal and five-marker negative phenotype (5NP), each with distinct underlying biology, we assessed the prognosis of FOXP3+ iTILs in these subtypes separately in a preplanned stratification.