Context: p53 tumor suppressor gene is a frequent target for mutations in a variety of tumors. The mutated gene is more stable than the normal gene and can be detected by immunohistochemical methods.
Aims: 1) To determine the expression of p53 immunohistochemically in a spectrum of benign, premalignant lesions and in various histological grades of oral squamous cell carcinoma
2) To verify if any correlation exists, between the localization and intensity of p53 staining pattern, and the degree of dysplasia.
Methods and Material: p53 expression was studied in 68 cases of oral lesions using immunohistochemistry (Dako cytomation). The location and intensity of staining was noted. Suprabasal positivity was considered as abnormal.
Results: All the benign lesions and low grade dysplasia were negative or showed only basal positivity. Suprabasal positivity increased from premalignant lesions (50%) to oral carcinomas (73.8%). In the premalignant category, intensity of p53 staining increased with increasing grades of dysplasia. In the malignant category, intensity of staining was stronger in the less differentiated tumors (68.4% vs 47.8%), while positivity was higher in better differentiated tumors (78.3% vs 68.4%). A small percentage of malignant tumors (21.4%) were negative. In 31% cases of SCC, the epithelium adjacent to the tumor which showed just hyperplasia/mild dysplasia on light microscopy, revealed suprabasal positivity.
Conclusions: Expression of p53 above the basal layer is an early event in oral carcinogenesis. Stronger staining (increasing grades of dysplasia) had greater risk of progressing into malignancy. p53 positivity is an early indicator of a developing carcinoma preceding morphological tissue alterations.
p53, oral cavity lesions, squamous cell carcinoma