We hypothesize that intrinsic expression of CTLA-4, PDCD1 (PD1), CD274 (PD-L1), PDCD1LG2 (PD-L2), CD276 (B7-H3), JAK2, and FoXO1 in neoplastic cells depends on BC immunophenotype, stem cell properties, and tumor microenvironment. This evidence concerns the gene PDCD1LG2 and breast cancer.