Immune checkpoint inhibitors targeting programmed cell death protein-1 (PD-1) and programmed death ligand-1 (PD-L1) are increasingly utilized in the treatment of various malignancies, including melanoma, non-small cell lung cancer, small cell lung cancer, liver cancer, alveolar soft part sarcoma, and hematologic cancers. The gene discussed is PDCD1; the disease is hematopoietic and lymphoid cell neoplasm.