The association between PD-L1 expression and JAK2V617F mutation was recently documented by Hara et al. in a patient with a coexisting JAK2V617F-positive ET and lung carcinoma in whom pembrolizumab (a drug directly blocking the interaction between PD-1 and its ligands, PD-L1, and PD-L2) treatment resulted in simultaneous normalization of the platelet count and a decrease of JAK2V617F VAF [85]. This evidence concerns the gene PDCD1LG2 and essential thrombocythemia.