P53 PROTEIN IMMUNOHISTOCHEMICAL EXPRESSION IN COLONIC ADENOMAS WITH AND WITHOUT ASSOCIATED CARCINOMA

Objectives: P53 protein immunohistochemical (MC) expression was invest igated in a series of colonic adenomas and carcinomas to determine the p53 immunohistochemical expression of adenomas in general compared wi th carcinomas, the difference in staining pattern between adenomas wit h associated carcinoma and those without associated carcinoma, and the difference in p53 staining in the usual adenomas (low-grade dysplasia ) compared with those harboring high-grade dysplasia. Methods: The stu dy involved a series of 20 adenomas without concurrent carcinoma (grou p 1 adenoma), 29 adenomas with concurrent carcinoma (group 2 adenoma), and 20 carcinomas. Sections of the paraffin-embedded tissues were sta ined with DO-7 p53 monoclonal antibody after microwave antigen-retriev al method. Cases with nuclear staining in greater than or equal to 20% of the tumor cells were considered positive. Results: Analysis of res ults showed that 65% of carcinomas and 37% of all adenomas were reacti ve with p53 LHC staining (p = 0.03), With respect to the adenomas, 30% of group 1 and 11% of group 2 adenomas were reactive for p53 protein (p = 0.42). Conclusions: Our data demonstrate a statistically signific ant higher p53 expression rate in colonic carcinomas than in adenomas, and that adenomas with concurrent carcinomas are more frequently p53 positive than those without concurrent carcinoma, but this was not sta tistically significant. Also, p53 expression is more frequent and inte nse in adenomas with high-grade dysplasia (10/20, 50%) than in ordinar y adenomas with low-grade dysplasia (8/29, 28%), which suggests a stro ng correlation between the degree of dysplasia in colonic neoplasia an d p53 expression pattern. (Am J Gastroenterol 1998;93:980-984. (C) 199 8 by Am. Cell. of Gastroenterology).