A Semiautomated Test for Microsatellite Instability and its Significance for the Prognosis of Sporadic Endometrial Cancer in Northern Norway

Abstract

Archival histologic material from 105 women (median age 62 years) treated for endometrial cancer was investigated for the replication error phenotype indicated by the observation of widespread microsatellite instability (MSI). Polymerase chain reaction (PCR) of DNA isolated from paraffin-embedded tissue was analyzed for MSI using six microsatellite loci with a fluorescent-based detection system. Flow cytometry and morphometric investigation were performed in the same material for each of the patients. Twenty percent (21 of 105) of screened endometrial cancers were found to have high MSI at two or more of the loci tested. The mean detection frequency per marker was highest in the dinucleotide repeat sequence, D2S123, and the mononucleotide repeat sequences amplified by Bat 25 and Bat 26. Death from endometrial cancer was not related to the occurrence of MSI (p=0.6). There was no significant association between MSI and FIGO stage (p=0.5), myometrial invasion depth (p=0.8), histological grade (p=0.3), or vessel invasion (p=0.5). There were, however, more MSI cases among the group of diploid cases compared with the aneuploid and tetraploid group. MSI is not a valuable prognosticator for survival of sporadic endometrial cancer, and diploid cases are significantly more often MSI positive than aneuploid and tetraploid cases.