CD274 and myeloproliferative neoplasm: The genes encoding the PD‐L1 (CD274, alias PD‐L1), PD‐L2 (CD273, alias PD‐L2), and JAK2 proteins are located in close proximity on the short arm of chromosome 9, which is often affected by copy number neutral loss of heterozygosity through the mechanism of acquired uniparental disomy (UPD) in MPN patients, usually leading to an increase in the JAK2‐V617F mutational burden.25