2026 MIPS Measure #491: Mismatch Repair (MMR) or Microsatellite Instability (MSI) Biomarker Testing Status

Percentage of surgical pathology reports for primary colorectal, endometrial, gastroesophageal or small bowel carcinoma, biopsy or resection, that contain impression or conclusion of or recommendation for testing of mismatch repair (MMR) by immunohistochemistry (biomarkers MLH1, MSH2, MSH6, and PMS2), or microsatellite instability (MSI) by DNA-based testing status, or both.

This measure is to be submitted each time a primary colorectal, endometrial, gastroesophageal or small bowel carcinoma, biopsy or resection surgical pathology examination is performed during the performance period. This measure may be submitted by Merit-based Incentive Payment System (MIPS) eligible clinicians who perform the quality actions described in the measure based on the services provided and the measure-specific denominator coding.

All surgical pathology reports for primary colorectal, endometrial, gastroesophageal or small bowel carcinoma, biopsy or resection

Patients regardless of age

AND

Diagnosis of primary colorectal, endometrial, gastroesophageal or small bowel carcinoma, biopsy or resection (ICD-10-CM): C15.3, C15.4, C15.5, C15.8, C15.9, C16.0, C16.1, C16.2, C16.3, C16.4, C16.5, C16.6, C16.8, C16.9, C17.0, C17.1, C17.2, C17.3, C17.8, C17.9, C18.0, C18.2, C18.3, C18.4, C18.5, C18.6, C18.7, C18.8, C18.9, C19, C20, C26.0, C54.1, C54.3, C54.8, C54.9, C55

AND

Patient procedure during the performance period (CPT): 88305, 88307, 88309

WITHOUT

Telehealth Modifier (including but not limited to): GQ, GT, POS 02, POS 10

AND NOT

DENOMINATOR EXCLUSION:

Patients with an existing diagnosis of Lynch Syndrome (ICD-10-CM): Z15.04, Z15.09, Z80.0, M1467

OR

Patients with an existing diagnosis of squamous cell carcinoma of the esophagus: M1192

OR

Hospice services provided to patient any time during the measurement period: M1191

Surgical pathology reports that contain impression or conclusion of or recommendation for testing of MMR by immunohistochemistry, MSI by DNA-based testing status, or both

Performance Met: Surgical pathology reports that contain impression or conclusion of or recommendation for testing of MMR by immunohistochemistry, MSI by DNA-based testing status, or both (M1193)

OR

Denominator Exception: Documentation of medical reason(s) surgical pathology reports did not contain impression or conclusion of or recommendation for testing of MMR by immunohistochemistry, MSI by DNA-based testing status, or both tests were not included (e.g., patient will not be treated with checkpoint inhibitor therapy, no residual carcinoma is present in the sample [tissue exhausted or status post neoadjuvant treatment], insufficient tumor for testing) (M1194)

OR

Performance Not Met: Surgical pathology reports that do not contain impression or conclusion of or recommendation for testing of MMR by immunohistochemistry, MSI by DNA-based testing status, or both, reason not given (M1195)

Detection of defective mismatch repair in colorectal carcinomas is important for detection of Lynch syndrome (hereditary nonpolyposis colorectal cancer syndrome [HNPCC]), which accounts for approximately 2 percent to 4 percent of all colorectal carcinomas and has clinical implications for treatment of the affected patient and family members (Sepulveda et al, 2017; Rubenstein et al, 2015). National Comprehensive Cancer Network (NCCN) recommends that all patients with a personal history of colon or rectal cancer should have MMR or MSI testing (NCCN, 2023). In the Molecular Biomarkers for the Evaluation of Colorectal Cancer guideline from the American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and American Society of Clinical Oncology it is recommended that mismatch repair status testing in patients with colorectal cancers is necessary for the identification of patients at high risk for Lynch syndrome and/or prognostic stratification (Sepulveda et al, 2017).

One of two different initial tests can be performed on colorectal specimens to identify individuals who might have Lynch Syndrome: 1) immunohistochemistry (IHC) for MMR protein expression, which is often diminished because of mutation; or 2) analysis for microsatellite instability (MSI), which results from MMR deficiency. NCCN guidelines state IHC and MSI on newly diagnosed colorectal and endometrial cancers regardless of family history to determine Lynch Syndrome, is cost effective and has been confirmed for colorectal cancer and endorsed by the Evaluation of Genomic Applications in Practice and Prevention (EGAPP) working group at the CDC, the US Multi-Society Task Force on Colorectal Cancer, and the American Gastroenterological Association (NCCN, 2022; NCCN, 2019).

References

Sepulveda AR, et al. Molecular Biomarkers for the Evaluation of Colorectal Cancer: Guideline from the American Society for Clinical Pathology, College of American Pathologists, Association for Molecular Pathology, and American Society of Clinical Oncology. Arch Pathol Lab Med. 2017 May;141(5):625-657.

Rubenstein, JH et al Diagnosis and management of Lynch syndrome. Gastroenterology. 2015 Sept: 149 (3):777-782. (Update to guideline in progress)

National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Colon Cancer. Version 2.2022. https://www.nccn.org/professionals/physician_gls/pdf/colon.pdf

National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Uterine Neoplasms. Version 1.2023. https://www.nccn.org/professionals/physician_gls/pdf/uterine.pdf