Mismatch Repair by Immunohistochemistry with Reflex to MLH1 Promoter Methylation

Also known as: MSI MLH1

Clinical Use

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

Not provided.

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.

Test Details

New York Approved

Methodology

Immunoassay (IHC)

Biomarkers

2 components

Mismatch Repair by Immunohistochemistry with MLH1 • IHCMLH1 Promoter Methylation • qPCR

Result Turnaround Time

1-5 days

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.