OVEREXPRESSION OF P53 PROTEIN IN SQUAMOUS-CELL CARCINOMA OF BUCCAL MUCOSA AND TONGUE IN TAIWAN - AN IMMUNOHISTOCHEMICAL AND CLINICOPATHOLOGICAL STUDY

Sixty squamous cell carcinomas of tongue and buccal mucosa were examin ed for expression of p53 protein by using an immunohistochemical techn ique improved by an antigen retrieval method. Twenty-seven (45%) tumor s demonstrated strongly positive staining. Thirteen of p53-positive tu mors (48%) also exhibited overexpression of p53 in immediately adjoini ng hyperplastic or pre-malignant epithelium. All 22 metastatic lymph n odes and 18 local recurrent lesions (except two) had an identical p53 immunophenotype to their corresponding primary sites. Mitotic indices were significantly higher in p53-positive tumors (P<0.01); however, no association of PCNA scores with p53 expression was found (P>0.1). The re was no correlation between p53 overexpression and tumor grade, size and staging, vascular invasion, lymph node metastasis, and early loca l recurrence. Overexpression of p53 was found to be relatively higher, although not statistically significant, in nonsmokers than in heavy s mokers (66.7% vs. 42.9%), and in non-betel-quid chewers than in heavy chewers (62.5% vs. 34.2%). These data are consistent with the hypothes is that inactivation of p53 protein may occur in the early phases of o ral tumorigenesis. It may not be a useful prognostic marker but could possibly be used for risk assessment and surveillance of local recurre nce.