Overexpression of p53 is an early event in the tumorigenesis of oral squamous cell carcinomas.

The purpose of this study was to determine the timing of p53 overexpression during the development of oral squamous cell carcinomas. Immunohistochemical analysis of p53 expression was performed on 107 cases of oral squamous cell carcinoma, 37 cases of leukoplakia, and 10 cases of cancer-free patient's normal oral mucosa samples. 43 of the 107 (40.2%) oral squamous cell carcinomas showed p53 overexpression. There was no relationship between p53-overexpression and clinicopathological factors, such as size of tumors, lymph node metastasis, hostological differentiation and prognosis. Overexpression of p53 was not detected in 10 normal mucosa. Seven out of 37 (18.7%) samples of leukoplakia and 15 out of 43 (34.8%) samples of noncancerous epithelium adjacent to the p53-positive carcinomas showed p53 overexpression, the results demonstrate that p53 protein may have an important role in the early stages of oral tumorigenesis.