Glossary Term:


microsatellite instability


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also called MSI. A type of genetic mutation often linked to hereditary non-polyposis colon cancer (HNPCC). This mutation causes size differences in sections of deoxyribonucleic acid (DNA) that are normally the same size in all a person’s cells. Testing for MSI is done on tissue taken from the cancer to find out if the DNA is of different lengths; if it is, HNPCC genetic testing is usually offered. See also deoxyribonucleic acid, genetic testing, hereditary non-polyposis colon cancer, mutation.