MMP9 and metastatic malignant neoplasm in the lymph nodes: However, we observed that the expression level of MMP9 was positively correlated with the status of lymph node metastasis (N classification) (N0-N1 vs. N2-N3) (P = 0.002), and clinical stage (I-II vs. III-IV) (P < 0.000) in NPC patients (Table 3).