Ki-67: a useful marker for the evaluation of dysplasia in ulcerative colitis

Aims-Evaluation of dysplasia in long standing ulcerative colitis is a diffi cult and often subjective task. Therefore, the aim of this study was to sea rch for a more objective parameter to help distinguish regenerative changes fi om epithelial dysplasia. Methods-A total of 97 sections from colectomy specimens from 12 patients wi th ulcerative colitis of more than 10 years duration were stained immunohis tochemically with MIB 1 to detect differences in the frequency and pattern of nuclei positive for the proliferation marker Ki-67. All patients had epi thelial dysplasia in one or more areas (high grade dysplasia, n=16; low gra de dysplasia, n=15; indefinite for dysplasia, n=16), and three patients had additional adenocarcinoma (one Dukes's C multifocal, mucinous carcinoma; o ne Dukes's C adenocarcinoma in the sigmoid; and one Dukes's A adenocarcinom a in the caecum). Two patients had adenomas-one had an 8 cm villous adenoma with intramucosal carcinoma, and the other had a 4 cm tubulovillous adenom a with high grade dysplasia. Results-There were highly significant differences between the percentages o f Ki-67 immunopositive cells in low grade and high grade dysplasia and carc inoma compared with regenerative epithelium. In high grade dysplasia and ca rcinoma, the distribution of Ki-67 positive cells was diffuse throughout th e full length of the crypt, whereas low grade dysplasia and epithelium inde finite for dysplasia, as well as regenerative epithelium, showed an expande d basal zone. Conclusions-Assessment of the number of Ki-67 immunostained cells is of add itional value in deciding whether the mucosa is regenerative or dysplastic, and the MIB I staining pattern is characteristic for most lesions with hig h grade dysplasia and carcinoma. Therefore, this technique could be combine d with routine histological evaluation of colorectal epithelium being exami ned for dysplasia.