p53 expression in ulcerative colitis: a longitudinal study.

p53 Mutation is a late event in the development of sporadic colorectal carcinoma (CRC). The timing of p53 mutations in the development of ulcerative colitis associated colorectal carcinoma (UCACRC) is, however, less certain and some reports suggest that it may be a relatively early event. This study sought to establish the timing of p53 mutations in neoplasia arising in ulcerative colitis. Blocks of 10 resected colorectal specimens from patients who had had a biopsy positive for dysplasia at least one year prior to resection were retrieved from the archives of St Mark's Hospital. Immunochemistry using the monoclonal antibody DO-7, specific for both mutant and wild type p53, was performed on sections from both the resection specimens and dysplastic biopsy specimens. Seven of the 10 resection specimens were positive for p53. Two of these seven specimens showed p53 overexpression in specimens taken two years before the development of carcinoma or high grade dysplasia. Five of the seven specimens were negative for p53 overexpression between one and four years prior to resection. These results suggest that p53 overexpression is usually a late event in the development of UCACRCs.