Microsatellite Instability Analysis

CPT: 81301; 88381

Updated on 08/1/2021

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Synonyms

Colorectal Cancer Screening
Hereditary Nonpolyposis Colorectal Cancer, Screening
Mismatch Repair Defect
Replication Repair (RER)

Special Instructions

This assay needs both (1) DNA prepared from FFPE (formalin-fixed and paraffin-embedded) tumor tissue and (2) matched normal tissue (FFPE or blood). Please provide a copy of the pathology report. This test will be delayed if the pathology report is not received. Please direct any questions regarding this test to customer service at 800-345-4363.

Expected Turnaround Time

10 - 14 days

Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.

Related Information

Specimen Requirements

Specimen

One paraffin-embedded tumor and either whole blood or paraffin-embedded normal tissue

Volume

Eight unstained slides at 5 μM and one matching H&E slide or FFPE tissue block or 3-5 mL whole blood

Minimum Volume

Samples with ≥4 mm² tumor and normal tissue surface area and ≥50% tumor content are preferred; 3 mL whole blood

Container

FFPE tissue block or slides, lavender-top (EDTA) tube, or green-top (sodium heparin) tube

Storage Instructions

Blocks and slides at room temperature; whole blood at 2°C to 8°C

Causes for Rejection

Tumor block containing insufficient tumor tissue or no tumor; broken or stained slides. Whole blood: Contaminated specimen; frozen whole blood received; leaking tube; clotted blood; hemolysis; specimen containing suspicious foreign material; quantity not sufficient for analysis

Test Details

Use

Identify tumors with microsatellite instability. High-frequency microsatellite instability (MSI-H) is associated with Lynch syndrome, but it is also found in 15% to 20% of sporadic colorectal and endometrial cancers. Lynch syndrome is an autosomal-dominant inherited cancer syndrome that predisposes to colorectal, endometrial, gastric, ovarian, upper urinary tract, and other cancers. MSI-High status may enhance the likelihood of tumor responsiveness to immune checkpoint inhibitor therapy.

Limitations

MSI-H is a marker of underlying DNA mismatch repair defect but does not define specific gene mutations responsible for cancers. If direct testing for gene mutations responsible for Lynch syndrome is desired, please call customer service at 800-345-4363 for more information. This assay can detect 8% to 12% of mutant in a background of wild-type genomic DNA.

This test was developed, and its performance characteristics determined, by LabCorp. It has not been cleared or approved by the US Food and Drug Administration (FDA).

Methodology

Multiplex polymerase chain reaction (PCR); capillary electrophoresis

References

NCCN Clinical Practice Guidelines in Oncology: Genetic/Familial High-Risk Assessment: Colorectal. Version 2.2015.