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DNA Repair· 2 min read

MSI-High vs TMB-High: Two Different Tumour Biomarkers

MSI-high and tumour-mutational-burden-high are both tumour biomarkers, but they measure different phenomena. MSI assesses instability at repetitive DNA regions; TMB counts mutations across a defined amount of sequenced DNA.

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Quick Answer

MSI-high and tumour-mutational-burden-high are both tumour biomarkers, but they measure different phenomena. MSI assesses instability at repetitive DNA regions; TMB counts mutations across a defined amount of sequenced DNA.

MSI-High vs TMB-High: Two Different Tumour Biomarkers: mechanism and interpretation mapThree connected stages summarise the article's mechanism, measured effect and interpretation boundary.MLH1 · MSH2 · MSH6 · PMS21Two MeasurementsMechanism2Why They Cannot Be SubstitutedObserved consequence3Key TakeawaysInterpret in contextGene or pathway evidence → measured phenotype → assay-aware conclusion
Mechanism map: the article’s main biological stages are separated from the final interpretation so a pathway relationship is not mistaken for a clinical conclusion.

Two Measurements

MSI can be assessed by molecular methods or inferred from mismatch-repair protein testing. TMB is assay-dependent and usually reported as mutations per megabase.

Why They Cannot Be Substituted

An MSI-high tumour may have high mutation burden, but the concepts and thresholds are distinct. Panel size, bioinformatic pipeline and tumour type affect TMB results.

Key Takeaways

  • ·MSI and TMB measure different features.
  • ·Assay and threshold are part of the result.
  • ·Neither biomarker should be inferred from the other.

Frequently asked questions

What is the key idea in MSI-High vs TMB-High: Two Different Tumour Biomarkers?

MSI-high and tumour-mutational-burden-high are both tumour biomarkers, but they measure different phenomena. MSI assesses instability at repetitive DNA regions; TMB counts mutations across a defined amount of sequenced DNA.

What should be kept with the result or mechanism?

MSI and TMB measure different features. Assay and threshold are part of the result. Neither biomarker should be inferred from the other.

References

  1. 1Tumour mutational burden as a biomarker. Nature Reviews Clinical Oncology, 2019. PubMed
  2. 2Mismatch repair and Lynch syndrome. Nature Reviews Cancer, 2017. PubMed
  3. 3FDA approval for MSI-H/dMMR colorectal cancer. FDA, 2026. Source

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