Oral lichen planus (OLP) is considered as a premalignant lesion, but some argue that only lichenoid lesions with dysplasia is precancerous. To address the question whether OLP without dysplasia is premalignant, we investigated the immunohistochemical expression of p53 in OLPs without dysplasia. Half of the OLPs showed p53 positive cells in the basal epithelium. SSCP-PCR analysis of 4 p53 positive OLPs failed to demonstrate mutations. What is the significance of p53 expression in these OLPs? The confinement of p53 positive cells to the basal cells seems to be against false positivity. Since the pathogenesis of OLPs involves cell-mediated cytotoxicity (CMC) which causes marked apoptosis, it is possible that the p53 expression represents wild-type p53 that may be regulating the apoptosis. Alternatively p53 protein may be stabilized by some mechanisms other than gene mutation as a result of cellular insults from CMC.

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