Here, using bioinformatics and statistical analysis on large series of publicly available breast cancer datasets [24, 25, 27], we formally evaluated the association between BRCA1- and BRCA2-deficiency with features of genomic instability, expression of PD-L1 and PD-1, landscape of inferred tumour-infiltrating immune cells, and T cell-inflamed gene expression signature in breast cancers. The gene discussed is PDCD1; the disease is breast cancer.