Finally, data on both PD-L2 and PD-L1, including their coexpression and distribution across cancer cells and infiltrating immune cell types, are expected to provide complementary value to the cancer cell PD-L2 marker in ER+ breast cancer, despite analytic performance issues of PD-L1 immunohistochemistry assays.38-43. This evidence concerns the gene PDCD1LG2 and breast carcinoma.