microsatellite stable
Tumor characteristic indicating intact DNA mismatch repair function and normal microsatellite sequences.
Full Definition
Microsatellite stable (MSS) describes tumors that maintain normal DNA mismatch repair function, resulting in stable microsatellite sequences throughout the tumor genome. MSS tumors contrast with microsatellite instability-high (MSI-H) tumors that have deficient mismatch repair mechanisms. This distinction has significant therapeutic implications, as MSS tumors typically do not respond to immune checkpoint inhibitors like pembrolizumab, while MSI-H tumors often demonstrate dramatic responses. MSS status is determined through PCR-based testing or immunohistochemistry for mismatch repair proteins.
Usage
Usage note: Often abbreviated as MSS in clinical documentation.
In Context
- "The tumor was confirmed to be microsatellite stable, making immunotherapy less likely to be effective." — Molecular pathology report
- "Microsatellite stable colorectal cancers typically require standard chemotherapy regimens." — Treatment planning discussion