Cases with high MMP9 expression showed strong invasion (T3–T4 vs T1–T2 = 63.1% vs 40.0%; P < 0.05) and metastasis (pN+ vs pN− =73.5% vs 37.7%; P = 0.001), and were clearly present in advanced ESCC stages (III–IV vs I–II = 78.9% vs 40.3%; P < 0.001) (Table 5). Here, MMP9 is linked to esophageal squamous cell carcinoma.