PLP2 was a high-risk myeloma gene. (a) PLP2 expression of NPC (n = 22), MGUS (n = 44), SMM (n = 12), and MM (TT2, n = 351; TT3, n = 208) in GSE5900 and GSE2658 datasets (∗∗p < 0.01, ∗∗∗p < 0.001). (b) A scatter plot showing the PLP2 expression in eight MM subgroups (CD1 and CD2 subgroups with spiked expression of CCND1 and CCND3; PR: proliferation; LB: low-bone disease; HY: hyperdiploid; MS: MMSET; MF: MAFB; MY: myeloid). (c) CD138 and PLP2 expressions in the bone marrow of NDMM patients. Representative case with a lack of PLP2 expression: H&E stain, CD138 immunostain, and PLP2 immunostain (upper row). Representative case with stable PLP2 expression: H&E stain, CD138 immunostain, and PLP2 immunostain (lower row).