[Ulcerative colitis-associated colorectal carcinoma. DNA ploidy as indicator of impending malignant transformation?]

The onset of a malignant transformation in long-standing ulcerative colitis is difficult to predict. The value of the clinical and histomorphological parameters in current use is limited. It was thus aim of the present study to investigate the value of DNA-ploidy for the early detection of a malignant transformation in long-standing ulcerative colitis. This retrospective study comprised 20 patients with long-standing ulcerative colitis. The average observation time was 7.3 years (range: four to twelve years). All patients took part in a surveillance program and had between four and seven colonoscopies within a minimum period of time of five years. At these instances mucosal biopsies were taken in a standardized manner at eight different locations throughout the colon. These paraffin-embedded specimens (n = 542) were analyzed histomorphologically and DNA-cytometrically. During the observation time five patients developed an ulcerative colitis-associated colorectal carcinoma (UCA). In these patients epithelial dysplasias were not more common than in the remaining 15 cases. The vast majority of the specimen of the patients with UCA showed distinct DNA-cytometrical alterations, i.e. they were aneuploid. Such aneuploid mucosal cell populations were distributed over the whole colon, irrespectively of the later site of the carcinoma. These aneuploid lesions were found in one case eleven years, in an average seven years prior to the final diagnosis of a UCA. In contrast, the colon epithelium of the patients without UCA showed only proliferative-diploid DNA-distribution patterns during the observation time. In summary, affected patients had multiple highly aneuploid lesions of the colon mucosa at an average of seven years prior to the final diagnosis of UCA. These lesions came from macroscopically chronic inflamed tissue, and where histomorphologically without signs of dysplastic transformation. DNA-cytometrical investigations could thus be of additional predictive value for the individual risk assessment as regards an impending malignant transformation.