It was found that positive staining of MMP-21 was detected in ESCC and positively correlated with deep tumor invasion, metastasis to lymph node, distant metastasis, and advanced TNM stage, which suggests that MMP-21 plays a promotive role in invasion and metastasis. Expression of MMP-21 in gastric, esophageal, and colorectal squamous cell carcinoma was estimated to be 60-70%, and the present study of OSCC shows strong expression of MMP-21 [18,21]. This evidence concerns the gene MMP21 and esophageal squamous cell carcinoma.