However, positive or high expression of NPM was significantly associated with advanced tumor stage (4 studies; III/IV vs. I/II; pooled OR = 5.21; 95%CI: 2.72–9.96; P < 0.001; random effects) and advanced differentiation grade (3 studies; poor vs. well/moderate; pooled OR = 1.82; 95%CI: 1.01–3.27 P = 0.046; random effects) (Figs. 3 and 4). Here, NPM1 is linked to neoplasm.