DNA aneuploidy in Crohn's disease and ulcerative colitis: results of a comparative flow cytometric study.

DNA ploidy and S-phase fractions were assessed by flow cytometry in colonic biopsy specimens from 28 patients with ulcerative colitis and 51 with Crohn's disease. Whereas only diploid DNA histograms were found in Crohn's disease and control subjects, three patients with ulcerative colitis exhibited DNA aneuploidy. In one case, aneuploidy was associated with low grade dysplasia. S-phase fractions were higher in ulcerative colitis (mean (SD) 17.8 (7.7)%) than in Crohn's disease (13.1 (4.6)%) or control subjects (14.2 (4.6)%), but did not correlate with either disease activity or duration in any group. In this study, aneuploidy was associated exclusively with ulcerative colitis, even in the absence of dysplasia. In view of the epidemiological differences in malignant colonic transformation between ulcerative colitis and Crohn's disease, this study suggests that flow cytometry may help to identify individuals with an increased cancer risk in ulcerative colitis.