Microsatellite Instability (MSI) [14989X]

Test Code

CPT Codes

Preferred Specimen
5 mL whole blood collected in an EDTA (lavender-top) tube and formalin-fixed, paraffin embedded tissue with tumor collected in formalin-fixed, paraffin embedded tissue block

Minimum Volume
Whole blood: 2 mL

Other Acceptable Specimens
Sodium heparin (green-top) tube • ACD solution B (yellow-top) tube • Formalin-fixed paraffin embedded tissue • Formalin-fixed paraffin embedded tissue with tumor


One formalin-fixed, paraffin embedded tissue with representative tumor and one EDTA whole blood from the same patient must be submitted for testing. Both sample types are required for testing.
One formalin-fixed, paraffin embedded tissue with representative tumor and one formalin-fixed paraffin embedded tissue with normal tissue. Avoid hemolysis.

Transport Temperature
Room temperature

Specimen Stability
Formalin-fixed paraffin block:
Room temperature: Indefinitely
Refrigerated: Indefinitely
Frozen: Unacceptable

Whole blood:
Room temperature: 8 days
Refrigerated: 8 days
Frozen: Unacceptable

Capillary Electrophoresis • Polymerase Chain Reaction (PCR)

FDA Status
This test was developed and its analytical performance characteristics have been determined by Quest Diagnostics. It has not been cleared or approved by the U.S. Food and Drug Administration. This assay has been validated pursuant to the CLIA regulations and is used for clinical purposes.

Setup Schedule
Set up: Wed, Sat; Report available: 4-5 days

Reference Range
See Laboratory Report

Clinical Significance
Patients with early onset and family history of colon cancers are suggestive of hereditary nonpolyposis colon cancer (hnpcc) syndrome. Microsatellite instability analysis on tumor tissue is recommended as a screening test to identify individuals eligible for germline mutation analysis or mismatch repair genes. Microsatellite instability analysis can also be used to identify adult and pediatric patients with unrespectable or metastatic solid tumors who have failed frontline therapy and who would be candidates for targeted immune therapy with Keytruda (Pembrolizumab).

Performing Laboratory
Quest Diagnostics Nichols Institute San Juan Capistrano
33608 Ortega Highway
San Juan Capistrano, CA 92675

The CPT Codes provided in this document are based on AMA guidelines and are for informational purposes only. CPT coding is the sole responsibility of the billing party. Please direct any questions regarding coding to the payor being billed. Any Profile/panel component may be ordered separately. Reflex tests are performed at an additional charge.