, Volume 5, Issue 1, pp 40-47
Date: 29 Jan 2009

Microsatellite instability in the evaluation of hereditary nonpolyposis colorectal cancer

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Hereditary nonpolyposis colorectal cancer (HNPCC) accounts for most hereditary colorectal cancers. The detection of families with HNPCC enables disease surveillance and clinical management, which significantly reduce morbidity and mortality. Mutations in DNA mismatch repair (MMR) genes underlie HNPCC and cause microsatellite instability (MSI). Although screening for pathogenic mutations in DNA MMR genes is time consuming and costly, MSI-based molecular diagnosis improves HNPCC diagnosis, which was once based on clinical characteristics and family history alone. Patients selected for MSI testing usually fulfill the Bethesda criteria. Tumor MSI status with tissue immunohistochemistry staining directs further genetic evaluation, including sequencing of MMR genes or methylation studies. This review outlines the importance of MSI status in disease diagnosis, prognosis, and treatment.