Interestingly, BRCA1-, but not BRCA2-, deficient breast cancer was associated with higher PD-L1 (CD274) expression compared to BRCA-proficient breast cancers in both WSI and TCGA cohorts (PBRCA1 = 5.6 x 10−6 and 0.014, respectively. Here, BRCA1 is linked to breast carcinoma.