MSI by PCR Analysis
Test Mnemonic
MSIID
CPT Codes
- 81301 - QTY (1)
Aliases
- Microsatellite Instability
- MSICCT
Performing Laboratory
Cleveland Clinic Laboratories
FDA Category
Laboratory Developed Test
Specimen Requirements
| Volume | Type | Container | Collect Temperature | Transport Temperature | Special Instructions |
|---|---|---|---|---|---|
| 10 mm square | Block, Formalin fixed paraffin | Formalin-fixed, paraffin-embedded block | Ambient | Ambient | Formalin-fixed paraffin-embedded tissue slides. Transport and store slides at ambient temperature. Three unstained sections FFPE tissue on charged, unbaked slides or scrolls, plus one H&E stained section with best tumor area circled by a pathologist. Provide the percentage of tumor cells present, minimum 10%. |
Stability
| Environmental Condition | Description |
|---|---|
| Ambient | FFPET slides and scrolls are stable at ambient temperature indefinitely |
| Refrigerated | FFPET slides and scrolls are stable refrigerated indefinitely |
| Frozen | Unacceptable |
Days Performed
Mon - Fri
Turnaround Time
3 days
Methodology
| Name | Description |
|---|---|
| Real-Time Polymerase Chain Reaction (RT-PCR) |
Special Info
Seven monomorphic biomarkers (ACVR2A, BTBD7, DIDO1, MRE11, RYR3, SEC31A AND SULF2) are analyzed to determine microsatellite status.
Clinical Info
The MSI ID PCR Analysis assay rapidly detects microsatellite instability (MSI) using seven monomorphic DNA markers evaluated by real-time PCR. This assay only requires a tumor sample; no matched normal sample is required for analysis. MSI represents a hypermutator phenotype caused by the loss of mismatch repair (MMR) gene function (MMR deficiency; dMMR). Tumor MSI-H/dMMR status can be due to germline genetic mutation (Lynch Syndrome) or, more commonly, somatic genetic and epigenetic changes. MSI testing is routinely indicated for any sporadic cancer type in the Lynch Syndrome spectrum (i.e., colorectal cancer, endometrial cancer, etc.) to screen patients for further work-up of germline alterations. Testing for MSI-H status is also indicated in advanced solid tumors, where it can predict the clinical benefit of immune checkpoint blockade for solid tumors, including colorectal cancer, endometrial cancer, and others.
Clinical Limitation
Specimens must contain at least 40% tumor cells; if less than 40% tumor is utilized, a negative result is of indeterminate significance. Tumor heterogeneity, tumor burden, specimen degradation, or other technology limitations may affect the sensitivity. Interfering substances, specifically formalin, decalcification agents, fixation agents containing heavy metals, or preservation of buffy coats using Hank’s Balanced Salt Solution (HBSS) can potentially affect assay performance. This test cannot distinguish between somatic and germline variants. Molecular microsatellite instability can be assessed by clinically validated IHC, PCR, and NGS methods; discrepancies between these results can occur due to technical or biological reasons. Test results obtained using this assay must be interpreted by healthcare professionals in conjunction with other clinical findings, family history, and other laboratory data.