CD274 and mismatch repair cancer syndrome 1: Currently, the US FDA‐approved companion diagnostic biomarkers linked to ICPI for breast cancer include PD‐L1 expression using the VENTANA PD‐L1 (SP142) IHC assay in TNBC for atezolizumab, TMB detected by CGP using the FoundationOne CDx assay for pembrolizumab, in addition to the identification of MSI/mismatch repair deficiency (dMMR) by multiple modalities for pembrolizumab.