Advanced
Technical
In the Industry Vocabulary Test
microsatellite instability
Also written as: MSI — Microsatellite Instability
Genetic marker indicating defective DNA mismatch repair, relevant for immunotherapy decisions.
Full Definition
Microsatellite instability (MSI) is a molecular phenotype resulting from defective DNA mismatch repair mechanisms, leading to the accumulation of mutations in repetitive DNA sequences called microsatellites. In gynecologic oncology, MSI testing is particularly relevant in endometrial carcinoma, where high MSI (MSI-H) tumors may be associated with Lynch syndrome and show enhanced response to immune checkpoint inhibitors like pembrolizumab.
Usage
Usage note: Specify MSI-H (high) vs. MSI-L (low) when reporting results.
In Context
- "Tumor testing revealed microsatellite instability-high status, suggesting mismatch repair deficiency." — molecular pathology report
- "The patient's MSI-H endometrial cancer was treated with pembrolizumab immunotherapy." — treatment plan
Also known as
MSI
mismatch repair deficiency
Contrasted with
microsatellite stable
MSS
Don't confuse with
chromosomal instability
DNA methylation