The expression of programmed death-ligand 1 (PD-L1) has been associated with profound responses to anti– programmed cell death protein (PD-1) therapy and led to several U.S. Food and Drug Administration approved PD-L1 diagnostic assays for melanoma, non–small cell lung cancer (NSCLC), and gastric, bladder, and cervical cancers [1,2,3,4]. This evidence concerns the gene CD274 and melanoma.