The KEYNOTE-756 phase III randomized trial (NCT03725059) is investigating the addition of pembrolizumab to NAT and standard adjuvant endocrine therapy in high-grade ER+ErbB2- breast cancer, but no gene expression profiling is being included in this trial [6]. Thus, we present a case of pCR to pembrolizumab and NAT in a postpartum ER+ErbB2- breast cancer patient with MammaPrint high-risk and BluePrint basal-type gene expression molecular profiling. Here, ESR1 is linked to breast cancer.