[Expression of protein p53 in the adenoma-colorectal carcinoma sequence]

To further evaluate the role of the p53 gene in the development of colorectal carcinoma we examined by immunohistochemistry p53 protein expression in a series of 136 colorectal adenomas, 25 adenomas containing early invasive carcinoma (pT1) and 160 advanced adenocarcinomas (pT3-pT4). p53 overexpression was detected in 22% of adenomas, 64% of adenomas with invasive carcinoma and 60% of advanced adenocarcinomas. In colorectal adenomas p53 expression was related to tumour size (P = 0.0013), histologic type (P < 0.0001) and grade of dysplasia (P < 0.0001). Only 7.5% of adenomas with low grade dysplasia were found to be p53 positive, whereas 73.3% of adenomas with high grade dysplasia demonstrated p53 overexpression. Most p53 positive adenomas and adenomas with invasive carcinoma showed intratumoural heterogeneity of p53 immunoreactivity. Conversely advanced adenocarcinomas were always uniformly p53 positive or negative. Our data show that p53 protein overexpression occurs at the transition from low grade dysplasia to high grade dysplasia, indicating a likely role for the p53 gene in the conversion of benign adenoma to malignant carcinoma.