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microsatellite instability
Genetic condition affecting DNA repair that influences cancer treatment selection.
Full Definition
Microsatellite instability (MSI) is a genetic condition resulting from defective DNA mismatch repair mechanisms. In cancer, MSI leads to accumulation of mutations and is particularly common in colorectal and endometrial cancers. Tumors with high MSI (MSI-H) typically respond well to immunotherapy, particularly PD-1 inhibitors, making MSI testing an important biomarker for treatment selection. The condition can be hereditary (Lynch syndrome) or acquired during cancer development.
Usage
Usage note: Often abbreviated as MSI; distinguish from chromosomal instability (CIN).
In Context
- "Testing revealed high microsatellite instability, making the patient eligible for pembrolizumab." — Molecular pathology report
- "Microsatellite instability analysis is now standard for all colorectal cancer patients." — Clinical guideline
Also known as
MSI
Contrasted with
microsatellite stability
Don't confuse with
microsatellite stability
chromosomal instability