Microsatellite-High
Tumor phenotype characterized by widespread instability in microsatellite DNA sequences due to mismatch repair deficiency.
Full Definition
A molecular classification describing tumors with high levels of microsatellite instability (MSI-H), typically resulting from defective DNA mismatch repair mechanisms. This phenotype is characterized by the accumulation of insertion and deletion mutations in repetitive DNA sequences called microsatellites throughout the tumor genome. MSI-H tumors are found in various cancer types including colorectal, endometrial, and gastric cancers, and can result from either germline mutations (Lynch syndrome) or somatic alterations in mismatch repair genes. The MSI-H phenotype is clinically significant as these tumors often respond well to immune checkpoint inhibitors and have distinct prognostic characteristics.
Usage
Usage note: Hyphenated form preferred; abbreviation MSI-H commonly used in clinical contexts.
In Context
- "The tumor was classified as microsatellite-high by PCR analysis of five microsatellite loci." — Pathology report
- "Microsatellite-high colorectal cancers showed superior response rates to pembrolizumab." — Clinical trial manuscript