ERBB2 and neoplasm: This upregulation of PD‐L1 coincides with an increased number of PD‐L1, PD‐1 and CTLA 4‐CD80/86 ligand‐receptor pairs between tumour cells and infiltrating T cells, particularly in the TNBC and HER2 subtypes, suggesting that checkpoint mediated crosstalk dampens anti‐tumour T cell activity and promotes radiotherapy resistance.