A study by Shibata [27] pointed out that COX-2 expression was correlated with the grade of oral dysplasia, and higher expression of COX-2 in severe dysplastic lesions than in mild and moderate dysplastic lesions was observed, verifying that COX-2 may be involved in the regulation of cell proliferation in the progression from normal mucosa to squamous cell carcinoma [28]. This evidence concerns the gene PTGS2 and squamous cell carcinoma.