PDCD1LG2 and aggressive NK-cell leukemia: PD-L1 expression on malignant NK cells was detected by immunohistochemistry in two of eight cases of EBV+ [64] and two of three cases of EBV− [65] aggressive natural killer-cell leukemia (ANKL), and copy number gains of PD-L1- and PD-L2-encoding genes were found in NK/T cell lymphoma (NKTCL) patients [66].