Since the expression of p53, bcl-2, COX-2, and Ki-67 in the studied OLP lesions was not significantly different from that in normal oral mucosa and the levels of the epidermal factor p63 were found to be even lower in these patients we can conclude that for the study cohort presented, there was no evidence of carcinogenesis. This evidence concerns the gene PTGS2 and oral lichen planus.