Microsatellite instability in long-standing ulcerative colitis

Objective. Ulcerative colitis (UC) is a chronic inflammatory disease of the colon associated with a high risk of developing colorectal cancer. Several genetic alterations have been documented in dysplasia and cancer developing in UC. Concerning microsatellite instability (MSI), many contradictory results have been published. We therefore analysed a large, well-characterized UC material for MSI to elucidate its significance in long-standing UC. Material and methods. From 33 patients, a total of 159 microdissected lesions and 165 mucosa samples obtained adjacent to the tissue blocks were analysed for MSI using the five standard markers recommended by the National Cancer Institute; D2S123, D5S346, D17S250, BAT-25 and BAT-26. In addition, 12 of the patients were investigated by a mini-satellite marker at the D1S7 locus. Results. High-level MSI (MSI-H) was detected in one villous adenoma with high-grade dysplasia and right-sided location. This represents 3.6% (1/28) of dysplastic mucosa investigated. No other lesions showed MSI in the five standard markers or at the D1S7 locus. Conclusions. This study suggests that MSI is rare in UC-related neoplasia as well as non-neoplastic lesions, and does not contribute to the development of dysplasia.