Mismatch Repair by Immunohistochemistry with Reflex to MLH1 Promoter Methylation
Also known as: MSI MLH1
Use
This test is used as a preferred reflex screening test for Lynch syndrome in non-colorectal cancer tumors, such as endometrial carcinoma. It involves immunohistochemical staining for mismatch repair proteins which acts as a surrogate test for microsatellite instability as measured by PCR. The test can help in both identifying microsatellite instability and guiding subsequent germline evaluation of mismatch repair genes for Lynch Syndrome (HNPCC) diagnosis. Abnormal results may also qualify patients for immune checkpoint inhibitor treatment.
Special Instructions
Include surgical pathology report and submit electronic request if possible. If you do not have electronic ordering capability, use an ARUP requisition form complete with an ARUP client number. Specimens must be accompanied by instructions for pathologist block selection or individual orders; otherwise, they will be held until clarification is provided. A Pathologist Block Selection Fee will be added if ARUP selects the block for testing.
Limitations
The test results need to be interpreted within the broader clinical context and in conjunction with other relevant clinical data. It is not intended to be used as a standalone diagnostic for malignancy or to detect minimal residual disease. Methylation at locations other than those covered by the primers and probes will not be detected, and methylation levels below 10 percent are reported as negative.
New York Approved
Methodology
Immunoassay (IHC)
Biomarkers
Result Turnaround Time
1-5 days
Related Documents
For more information, please review the documents below
Specimen
Tumor Tissue (FFPE)
Volume
Not provided
Minimum Volume
Not provided
Collection Instructions
Formalin fix (10 percent neutral buffered formalin is preferred) and paraffin embed tissue. If sending precut slides, do not oven bake. Transport tissue block or 15 unstained (3-5 micron thick sections), positively charged slides in a tissue transport kit (ARUP supply #47808).
Storage Instructions
Room temperature or refrigerated. Ship in cooled container during summer months.
Causes for Rejection
Paraffin block with less than 25 percent tumor tissue. Specimens fixed in any fixative other than 10 percent neutral buffered formalin. Decalcified specimens.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | Indefinitely |
| Refrigerated | Indefinitely |
| Frozen | Unacceptable |