PDCD1 and breast cancer: Although immunotherapy with anti-PD-1 in BC has primarily been used for TNBC cases, considered the most immunogenic subtype, our analysis of immune features in patients’ biopsies from TNBC, ER+ and HER2+ BC subtypes, revealed comparable frequencies of infiltrating CTLs and similar PD-L1 expression across all subtypes (Supplementary Figure S11), at least at the biopsy level.