JAK2 and myeloproliferative disorder: As PD‐L1 and JAK2 are both located on the 9p24.1 locus (320 kb apart; Figure 1C), we hypothesized that the presence of chromosome 9p UPD has an effect on the observed PD‐L1 expression in MPN cells, which would explain why MPN cells in patients with PV have higher PD‐L1 expression levels compared to other disease entities.