MSI Analysis
GENERAL INFORMATION
Test Name:
Microsatellite Instability (MSI) Analysis
Methodology:
Polymerase chain reaction (PCR)
Days of Week Performed:
M,Tu, W, Th, F
Routine TAT:
24 hours (excluding weekends and holidays)
Reference Range:
Reportable range for the assay is Microsatellite stable (MSS) or Microsatellite instability- High (MSI-H)
Clinical Utility:
Microsatellite instability (MSI) testing can be used to assist in treatment decisions and screen for Lynch syndrome/hereditary nonpolyposis colorectal cancer (HNPCC). A microsatellite stable (MSS) phenotype suggests the presence of normal DNA mismatch repair function within the tumor. A MSI-High phenotype indicates defective DNA mismatch repair (dMMR). MSI-High (MSI-H) tumors may respond to treatment with immune checkpoint inhibitors. The presence of MSI-H may also be an indication for additional testing/genetic counseling for Lynch syndrome. The MSI results should be considered in conjunction with other clinical information.
Collection Instructions:
Tumor Tissue: Formalin fix (10 percent neutral buffered formalin) and paraffin embed tissue (FFPE). Testing can be performed off FFPE tissue block or utilizing an unstained 5 micron slide. Testing requires at least 10% neoplastic cellularity.
Specimen Transport Requirements:
Room temperature. Protect tissue block from excessive heat.
Rejection Criteria:
Specimens not meeting neoplastic cellularity requirements. Specimens fixed/processed in alternative fixatives. Decalcified specimens.
Specimen Retention Time:
In house FFPE block retention follows College of American Pathologists (CAP) requirements.
