Deregulated expression of immune checkpoint molecules, such as the immune checkpoint inhibitors (ICIs) PDCD1 (PD-1) and CD274 (PD-L1), in adjacent nontumor liver tissues from LM patients, including colorectal cancer, ovarian cancer, breast cancer, nasopharyngeal carcinoma, kidney cancer, and cervical cancer liver metastases, was validated by immunohistochemistry (IHC) staining. This evidence concerns the gene PDCD1 and breast cancer.