[Immunohistochemical distribution of p53 and Ki-67 in 2 cases of colorectal carcinoma occurring in ulcerative colitis].

We studied immunohistochemically the distribution of p53 overexpression and Ki-67 as a marker of cell proliferation, in 2 cases of advanced colorectal carcinomas occurring in UC, in comparison with histopathological features such as carcinoma and dysplasia. One is a case of 4 independent colorectal carcinomas surrounded by widespread dysplasia, and the other is a case of solitary rectal carcinoma. In these 2 cases, formalin-fixed paraffin-embedded tissues covering all of the resected specimens were examined for p53 and Ki-67 immunoreactivity using microwaving technique. p53 was negative in normal mucosa and inflammative mucosa without dysplasia. p53 was strongly positive in cancerous lesions except one lesion, and various degrees of dysplasia surrounding these lesions also showed p53 positive. The numbers of p53 and Ki-67 positive cells were higher in severe dysplasia than in mild dysplasia. Some areas of the dysplastic mucosa histologically represented "hyperplastic pattern of villous feature." In these areas p53 positive cells were aggregated in the basal part of the villous crypt, and the number of Ki-67 positive cells per gland was larger than in normal gland. Our examination covering the whole mucosa revealed: 1) p53 and Ki-67 are useful diagnostic markers for grading the degree of dysplasia. 2) Positivity of immunoreactive p53 in dysplasia seems to be consistent with that in cancers occurring in the surrounding dysplastic area in most of our cases.