MMP9 and metastatic malignant neoplasm in the lymph nodes: Meanwhile, MMP9 overexpression was found to be associated with higher histological grades (grade 3 vs. 1–2, OR = 1.77, P < 0.001), larger tumor size (for > 2 cm vs. ≤2 cm, OR = 1.32, 95% CI 1.13–1.54, P < 0.001; for > 5 cm vs. ≤5 cm, OR = 2.02, 95%CI 1.28–3.17, P = 0.002; Fig. 5), lymph node metastasis (OR = 2.90, P < 0.001), and positive HER2 (OR = 1.41, P = 0.021).