In primary mediastinal large B-cell lymphoma [21], Hodgkin's lymphoma [21, 22], gastric cancer [23], and triple-negative breast cancer [24], the amplification of chromosome 9p24.1 containing the PD-L1 and PD-L2 genes as well as Janus kinase 2 (JAK2) is known; this suggests that the activation of JAK-STAT signaling may be partially involved in subsequent changes experienced by cells possessing this focal amplification. The gene discussed is PDCD1LG2; the disease is gastric cancer.