Clinical and pathologic significance of microsatellite instability in endometrial cancer.

Microsatellite instability (MSI) is identified as electrophoretic shifts in allele sizes of microsatellite DNA sequences. It is characteristic of a subset of sporadic colorectal tumors as well as hereditary nonpolyposis colorectal cancer (HNPCC). The cells that display MSI are thought to be susceptible to increased mutability. MSI has been detected in a wide variety of human tumors, but the influence of this form of genetic instability on disease initiation and progression remains unclear. Using a polymerase chain reaction (PCR)-based method we screened 50 sporadic primary endometrial carcinomas to characterize the prevalence of MSI in these tumors and analyze the correlation of MSI with clinicopathologic parameters in this malignancy. Fifteen cases (30%) displayed low frequency of MSI (MSI-L) showing MSI at one locus in 5 loci examined. Two cases (4%) showed high frequency of MSI (MSI-H) having MSI at 2 or more loci. Taking MSI-L and MSI-H cases together as MSI-positive, statistical analysis of patient age, tumor grade, and stage failed to disclose significant differences or trends between cases with MSI-positive and MSI-negative (P > 0.05). No significant relationship was observed between patients with MSI and without MSI (P > 0.05), however, the MSI exhibited only in those cases without evidence of disease at the 24th month after treatment. The difference is statistically significant when compared with patients who are alive with disease or died of disease (P < 0.01). However, the overall survival curves were not statistically different. We conclude that MSI is present in a subgroup of endometrial cancer.