MIPS quality measure 491 requires that a biopsy or resection report for colorectal, gastroesophageal, endometrial, or small bowel carcinoma include an impression or recommendation for mismatch repair (MMR) testing by immunohistochemistry (MLH1, MSH2, MSH6, PMS2) or microsatellite instability (MSI) testing, or both.
This information should be on the original pathology report. While many cases include this documentation, it is often added later through amendments. Since data is regularly submitted to registries, it's best to include a reference to the intended testing in the original report.
2025 UPDATE: As the author of this measure, CAP has clarified that all specimens diagnosed as squamous cell carcinoma can be excluded from this requirement with the assumption that MMR/MSI testing is not needed as it does not inform patient care. Previous to 2025, only esophageal squamous cell specimens were pre-approved for exclusion from the requirement. APS appreciates the feedback we received from several clients regarding squamous cell cases not requiring this type of testing.
Anywhere on the original report, if MMR/MSI testing is likely to be or has already been performed, include a statement to indicate this. Example:
“MMR/MSI testing will be performed as indicated for specimen A”
“MMR/MSI testing to follow in an amendment.”
“MMR/MSI testing not recommended due to ___”
“MMR/MSI testing performed on previous specimen and not repeated.”
MMR/MSI can be replaced with any of the following terms:
Mismatch repair, microsatellite instability
Results can be documented but are not required. Statements such as the above, indicating the impression of or recommendation for testing, qualify the case as “met” per CMS guidance.
We will continue to monitor developments to this and all quality measures in the MIPS program.
