CD274 and leukoplakia: Broadly, both PD-L1 expression as defined by CPS (dysplastic epithelium and other immune cells) or TPS (epithelial dysplastic cells) was significantly increased among proliferative leukoplakia samples compared with localized leukoplakia (CPS, 2.45 vs. 0; localized leukoplakia: 0.1 vs. 0; both P < 0.0001), but notably values for both were frequently measured at 1 or less (78.1%).