ABSTRACT
PURPOSE: Many studies have demonstrated that sporadic MSI-H colorectal cancers share several clinicopathological features with hereditary nonpolyposis colorectal cancers. However, microsatellite instability (MSI) in HNPCC and sporadic colorectal cancer occur through two different mechanisms. The aim of this study was to define the clinicopathological significance of MSI in sporadic colorectal cancers. METHODS: Using paraffin-embedded specimens from 291 consecutive sporadic colorectal cancer patients, a total of 5 microsatellite markers (D2S123, D5S346, D17S250, BAT25 and BAT26) were used to evaluate the MSI status. Age, gender, tumor size, site, grade, stage, vascular invasion and CEA level were evaluated. RESULTS: The incidence of MSI-H was 7.9% (23/291) in sporadic colorectal cancer. These were more likely to be right-sided (56.5% vs 17.5%, P<0.05) and poorly differentiated (31.8% vs 5.5%, P<0.05), compared with microsatellite stable cancers. However, there was no significant difference according to gender, tumor size, grade, stage, and vascular invasion. MSI-H cancers had a tendency for an earlier age and lower CEA level but this did not reach statistical significance. CONCLUSION: These results suggest that sporadic MSI-H colorectal cancers are more likely to be right-sided, and poorly differentiated. Although sporadic MSI-H colorectal cancers show MSI as with HNPCC, the carcinogenesis and clinicopathological features are different from those of HNPCC. Additional more study will be needed to further define the role of MSI in the survival and adjuvant chemotherapy of sporadic colorectal cancer.