CAP–AMP MMR / MSI Testing Guideline
Testing tumours for mismatch-repair deficiency and microsatellite instability to inform immunotherapy and screening.
Standards for testing mismatch-repair (MMR) and microsatellite instability (MSI) status.
What it is
A guideline from the College of American Pathologists (CAP), developed with the Association for Molecular Pathology (AMP) and partners, on testing tumours for mismatch-repair (MMR) deficiency and microsatellite instability (MSI).
Why it matters
MMR / MSI status can indicate whether a tumour may respond to immune checkpoint inhibitor (immunotherapy) treatment, and can flag cases that warrant screening for Lynch syndrome. It is most established in colorectal and endometrial cancers but is relevant across tumour types.
Key points
- Assesses mismatch-repair (MMR) proteins by IHC and/or MSI by molecular methods
- Informs eligibility for immune checkpoint inhibitor (immunotherapy) treatment
- Helps flag cases for Lynch syndrome screening
- Most established in colorectal and endometrial cancers
How our reporting uses it
When MMR / MSI testing is requested, our reporting reflects these principles so results are clear for both treatment and screening decisions.
Keep reading
Related department: Histopathology · Molecular Diagnostics
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