MSI-High & dMMR
Colorectal Cancer
If your report says MSI-high or dMMR, call us. We can help you identify the records and questions to bring to a treatment review.
Mismatch-repair and microsatellite-instability results can affect immunotherapy decisions and may also raise questions about inherited cancer risk.
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Tell us what you are facing. Our Patient Care Team will follow up personally and explain the next step. The introductory call is free.
MSI-high and dMMR are related findings with practical treatment implications
Mismatch repair is a cellular system that corrects certain DNA-copying errors. When the system is deficient, a tumor may accumulate characteristic changes called high microsatellite instability. Reports may use dMMR, MSI-H or both, depending on the test performed.
How the result may be measured
Mismatch-repair proteins
Immunohistochemistry can evaluate whether key mismatch-repair proteins are present or absent in tumor tissue.
Microsatellite instability
DNA-based methods can evaluate instability at specific regions. Results and terminology should be interpreted with the pathology and clinical setting.
Why MSI-H or dMMR can change systemic-treatment options
MSI-high or dMMR colorectal cancers can be more responsive to immune-checkpoint therapy than mismatch-repair-proficient tumors. The treatment setting, disease stage, symptoms, autoimmune history, organ function and previous therapy still matter. A biomarker is important, but it does not replace a complete clinical review.
Some results warrant evaluation for Lynch syndrome
An abnormal mismatch-repair result can be caused by an inherited condition or by changes limited to the tumor. Additional tumor testing, family history review, genetic counseling or germline testing may be discussed. The result can matter not only to the patient but also to relatives.
Verify that the result and the clinical setting match
- Which test was performed?
- Was the tissue adequate?
- Which proteins were absent, if any?
- Is there metastatic or localized disease?
- Are there autoimmune or transplant considerations?
- Has genetic counseling been discussed?
Continue with the part of your diagnosis that matters now
Talk with our Patient Care Team for free
If you are facing MSI-high or dMMR colorectal cancer, you do not have to sort through the reports and options alone. Tell us what you are facing. We can explain the consultation process and help you decide whether a physician review at Sunridge may be an appropriate next step.
Frequently asked questions
Are MSI-high and dMMR the same?
They describe related biology and often overlap, but they may be measured by different methods. A pathology or oncology team can interpret discordant results.
Does MSI-high guarantee immunotherapy will work?
No. It can substantially increase the relevance of immunotherapy, but no biomarker guarantees response or eliminates the need to review risks and the full clinical situation.
Does dMMR mean I have Lynch syndrome?
Not necessarily. Some dMMR tumors are sporadic. Genetic counseling and additional testing can help determine whether an inherited condition is likely.
Sources and important context
- Colon Cancer Treatment (PDQ®)
- Rectal Cancer Treatment (PDQ®)
- Biomarker Testing for Cancer Treatment
- Finding Cancer Care and Seeking a Second Opinion
- Cancer Therapy Interactions With Foods and Dietary Supplements
Medical information disclaimer: This page is for education and does not diagnose cancer or recommend a treatment plan. Treatment decisions require review of the exact diagnosis, stage, pathology, biomarkers, prior treatment, medications and overall health. No therapy is appropriate for every patient, and no supplement, diet or complementary treatment should be assumed to replace medically indicated cancer care.