PSME3 and lung cancer: We concluded that when the cutoff values of Ki and Ki/K1 were 0.022 ml/g/min and 0.093, respectively, there was a good diagnostic value in the differential diagnosis of metastasis and non-metastasis in FDG-avid LNs of lung cancer, especially improving the specificity (AUC of 0.672 and 0.673, and specificity of 0.918 and 0.776, respectively).