MMP1 and esophageal squamous cell carcinoma: While no significant correlations were proven between serum MMP-1, − 2, and − 9 concentrations and lymph node status in head and neck SCC [50], serum MMP-2 was found to be correlated with lymph node involvement in laryngeal SCC [45], and serum MMP-13 levels were associated with esophageal SCC lymph node metastasis [42].