PDCD1 and breast carcinoma: 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.