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Mismatch Repair Mechanism (MMR) by Immunohistochemistry

MMR for Colon Cancer, Immunohistochemistry for Colon Cancer.

Department

Advanced Diagnostics

Specimen Collection Criteria

Collect: Paraffin-embedded tissue. A paraffin block must be submitted. Submit formalin-fixed, paraffin-embedded block with corresponding H&E slide. Tissue should be well fixed and well processed.

The specimen must be accompanied by a completed requisition and must contain the patient name, date of birth, collection date, ordering physician, and source of specimen.

Physician Office/Draw Specimen Preparation

Maintain paraffin-embedded tissue at room temperature (20-26°C or 68-78.8°F) until transport. 

Preparation for Courier Transport

Transport: Paraffin-embedded tissue, at room temperature (20-26°C or 68-78.8°F). 

Rejection Criteria

• Tissue in fixatives other than 10% formalin or zinc formalin.
• Improper labeling, inadequate information.

Inpatient Specimen Preparation

Please refer to Surgical Specimen, Routine in the Beaumont Laboratory Test Directory.

In-Lab Processing

Maintain specimens at room temperature (20-26°C or 68-78.8°F) until testing. 

Storage

Specimen Stability for Testing:

Room Temperature (20-26°C or 68-78.8°F): Indefinitely 
Refrigerated (2-8°C or 36-46°F): Unacceptable 
Frozen (-20°C/-4°F or below): Unacceptable 

Specimen Storage in Department Prior to Disposal: 

Room Temperature (20-26°C or 68-78.8°F): 7 days 

Laboratory

Royal Oak Anatomic Pathology – Advanced Diagnostics Laboratory.

Performed

Every other business day. Results available in 7 business days.

Reference Range

No loss of nuclear expression of MMR proteins: No immunohistochemical evidence of deficient mismatch repair (low probability of microsatellite instability-high [MSI-H]).

Loss of nuclear expression of one or more MMR proteins – deficient mismatch repair.

Test Methodology

This immunohistochemical assay was developed and its performance characteristics determined by the Beaumont Health System Advanced Diagnostic Laboratory. It has not been cleared or approved by the US Food and Drug Administration. The FDA has determined that such clearance is not necessary. This assay can be used for clinical purposes. It should not be regarded as investigational or for research only.

Interpretation

• NO LOSS OF NUCLEAR EXPRESSION OF MMR PROTEINS: NO IMMUNOHISTOCHEMICAL EVIDENCE OF DEFICIENT MISMATCH REPAIR (low probability of microsatellite instability-high [MSI-H]).
• LOSS OF NUCLEAR EXPRESSION OF MLH1 AND PMS2: DEFICIENT MISMATCH REPAIR.
• LOSS OF NUCLEAR EXPRESSION OF MSH-2 AND MSH-6: DEFICIENT MISMATCH REPAIR.
• LOSS OF NUCLEAR EXPRESSION OF PMS2: DEFICIENT MISMATCH REPAIR.
• LOSS OF NUCLEAR EXPRESSION OF MSH6: DEFICIENT MISMATCH REPAIR.

Clinical Utility

Loss of protein expression is associated with loss or suppression of DNA mismatch repair complex. 

CPT Codes

Technical: 88341x3, 88342.

Contacts

Last Updated

9/29/2022