Sequential immunohistochemical p53 expression in biopsies of oral lichen planus undergoing malignant evolution.

Transformation in squamous cell carcinoma (SCC) may occur in a small percentage of patients affected by oral lichen planus (OLP), but the pathogenesis remains to be elucidated. Overexpression of p53 protein was investigated immunohistochemically in 28 cases of OLP, followed up by sequential biopsies for up to 96 months. In 15 cases (Group 1), no dysplastic changes or neoplastic transformation occurred during the follow-up period; in 7 cases, OLP and SCC were synchronously observed (Group 2), whereas in another 6 cases (Group 3) SCC developed several months or years after diagnosis of OLP. The percentage of p53-positive epithelial cells at first diagnosis was significantly higher in the cases of Groups 2 and 3 than in those of Group 1. In contrast, evaluation of growth fraction by MIB-1 monoclonal antibody did not show any statistical differences among the three groups. Although no conclusions can be drawn about the molecular pathway leading to neoplastic transformation of OLP, or about the role of p53, the results indicate that immunohistochemical evaluation of p53 expression may be a practical tool to select cases of OLP with a high risk of neoplastic transformation.