Microsatellite Instability Analysis (MSI)

Assay Description

PCR and fragment analysis of paired normal and tumor tissue to determine microsatellite instability (MSI) at the standard five NCI-recommended loci. Positive results are reported as MSI-high (at least two markers are unstable) or MSI-low (one marker is unstable).

Specimen Requirements

•Note: An additional patient sample from normal, non-tumor tissue is required for comparison testing in MSI Analysis. Please submit all specimens with one test requisition form.

•Specimen requirements for normal tissue in order of preference are: 1) 5 mL peripheral blood in EDTA tube OR 2) FFPE tissue slides or block containing only non-tumor tissue. Please label these as "normal tissue". OR 3) In cases where no alternative tissue is available, we can attempt to isolate non-tumor tissue from the tumor specimen submitted. Note “Use tumor sample for normal tissue” on requisition. See requirements below.

•Specimen requirements for tumor tissue: FFPE tissue: Paraffin block is preferred. Alternatively, send 1 H&E slide plus 5-10 unstained slides cut at 5 or more microns. Please use positively-charged slides and 10% NBF fixative. Do not use zinc fixatives.

Storage and Transport

Use cold pack for transport, making sure cold pack is not in direct contact with specimen. Slides can be packed at room temperature.

Specimen Rejection Criteria

All specimens must be submitted according to the test directory instructions.  Before submitting specimen, please carefully review specimen requirements.

Listed below are possible causes for delays in specimen processing or possible specimen rejections or cancellations:

• No patient identification on requisition form
• No patient identification on specimen container or slides
• No referring provider
• No account information provided
• No test ordered on requisition
• No specimen source provided
• Inappropriate specimen type
• Insufficient volume for analysis
• Inappropriate specimen container
• Improper specimen transport
• Specimen leaked in transport
• Specimen submitted in incorrect or expired transport media
• Slides broken beyond repair on receipt
• Conflict between patient name on specimen and requisition form
• Specimen not properly preserved
• Sample containing a needle

A representative from Client Services will attempt to contact your office  to resolve specimen problems.  Additional documentation may be requested from your office to be returned by fax.  In the event that resolution is not possible, the specimen may be returned to your office.

Turn Around Time (TAT)

7 Days.

CPT Codes*

81301