Background: Ulcerative colitis (UC) is a chronic inflammatory disease of the colon characterized by repeated episodes of inflammation and epithelial regeneration. Patients with long-standing UC have an increased risk for the development of dysplasia and subsequent colon carcinoma. Because dysplasia likely results from deregulatec cell proliferation, the authors examined Ki-67 immunoreactivity in tissues from UC patients to examine patterns of proliferation in neoplastic and nonneoplastic lesions.
Methods: One hundred and eighty-seven specimens were obtained from 41 patients with UC and each lesion evaluated according to the International Classification for Dysplasia in Inflammatory Bowel Disease. All sections were stained with a monoclonal antibody directed against the proliferation marker Ki-67, and evaluated by three observers.
Results: Statistically significant differences in the pattern of Ki-67 immunoreactivity were observed between nonneoplastic and neoplastic lesions. In regenerative mucosa, Ki-67 immunoreactivity localized to the bases of the crypts, and the proliferative zone appeared expanded. In dysplasia, Ki-67 staining was prominent in cells in the superficial mucosa, as well as in cells at the crypt bases. In some dysplasias and all invasive carcinomas, Ki-67 staining was diffusely distributed throughout the crypts, suggesting complete deregulation of normal cell proliferation.
Conclusions: Cell proliferation is markedly increased in patients with UC, and appears abnormally regulated in neoplastic lesions. Furthermore, Ki-67 staining helps delineate areas of dysplasia in cases in which the distinction from regenerative mucosa is unclear. The increased cell proliferation that occurs in patients with UC may predispose the mucosa to mutational events, thereby increasing cancer risk in these patients.