Microsatellite Instability
General Information
Lab Name
Microsatellite Instability
Lab Code
MSI
Epic Name
Order using "UW Genetics and Solid Tumor Test Request"
See tip sheet for more information (internal link).
Description
MSI testing and/or immunocytochemistry for mismatch repair proteins MLH1, MSH2, MSH6, and PMS2 should normally be ordered first as part of initial testing (screening) for possible defects in the DNA mismatch repair system. Testing for mutations in the mismatch repair genes is available as a separate test. MSI immunohistochemistry can be concurrently ordered on the same sample.
Defective mismatch repair results in inaccurate copying of repetitive DNA sequences during cell division, causing alterations in the length of short tandem repeat regions (microsatellites) in tumor DNA. This is detected by analyzing the length of a panel of microsatellite sequences using Illumina sequencing (Salipante 2014).
Indications for MSI Testing
- Guide treatment with checkpoint blockade immunotherapy
- Workup of possible Lynch Syndrome (HNPCC)
- Workup of possible Muir-Torre Syndrome in patients with sebaceous neoplasms
- Prognosis in sporadic colorectal cancer
Follow up testing for MSI positive tumors when Lynch Syndrome is suspected
BRAF Mutations [BRAF] V600E mutations are present in about 50% of sporadic MSI colorectal cancer and are absent in Lynch Syndrome.
Lynch Syndrome Workup
Defects in DNA mismatch repair resulting in MSI are present in hereditary non-polyposis colorectal cancer (HNPCC, Lynch syndrome), as well as variants such as Muir-Torre syndrome, and in about 10-15% of sporadic colorectal cancers as well as numerous additional cancer types.
Muir-Torre Syndrome (MTS) is a rare variant of Lynch syndrome (HNPCC) characterized by the additional presence of sebaceous neoplasms. Given that 30-60% of patients presenting with sebaceous neoplasms have Muir-Torre Syndrome (Abbas et al. 2009) and that cutaneous manifestations are the first neoplasm diagnosed in 20% of patients with said syndrome (Ponti et al. 2005), it is suggested that microsatellite instability testing be performed in all patients with sebaceous neoplasms, regardless of family history.
Cancer Treatment with Immunotherapy
MSI is also used to guide treatment with checkpoint blockade immunotherapy in patients with advianced cancer. The U.S. FDA has approved the use of pembrolizumab for adult and pediatric solid tumors with MSI in patients with unresectable or metastatic cancers that have progressed following prior treatments and who have no satisfactory alternative treatment options OR in colorectal cancer with MSI that has progressed following treatment with a oxaliplatin, fluoropyrimidine, and irinotecan.
References
- Salipante SJ, et al. Microsatellite instability detection by next generation sequencing. Clin Chem. 2014, 60:1192. PMID 24987110
- Cicek MS, et al. Quality assessment and correlation of microsatellite instability and immunohistochemical markers among population- and clinic-based colorectal tumors results from the Colon Cancer Family Registry. J Mol Diagn 2011, 13:271-81. 21497289
- Abbas O and Mahalingam M. Cutaneous sebaceous neoplasms as markers of Muir-Torre syndrome: a diagnostic algorithm. J Cutan Pathol 2009, 36:613-9. 19515040
- Ponti G and Ponz de Leon M. Muir-Torre syndrome. Lancet Oncol 2005, 6:980-7. 16321766
- Le DT, et al. PD 1 Blockade in Tumors with Mismatch Repair Deficiency. N Engl J Med. 2015, 372:2509. PMID 2602825
Synonyms
checkpoint blockade, colon cancer, Gynecological Oncology Pathway, GYNPTH, hereditary nonpolyposis colorectal cancer, HNPCC, immunotherapy, Lynch syndrome, mismatch repair, MLH1, MSH2, MSH6, pembrolizumab, PMS2, prostate, THOR, THORplex
Components
| Code | Name |
|---|---|
| MSIRE | MSI Result |
| MSICH | MSI Clinical History |
| MSIIN | MSI Interpretation |
| MSIMT | MSI Methods |
| MSIDI | MSI Director |
Interpretation
Method
Microsatellite loci are analyzed by Illumina next-generation sequencing (Salipante 2014). The panel of loci includes the BAT25, BAT26, NR21, NR24, and MONO27 microsatetllite regions. This test was developed and its performance characteristics determined by the Department of Laboratory Medicine at the University of Washington.
Reference Range
See individual components
Ref. Range Notes
Microsatellite stable.
No instability detected.
Guidelines
Ordering & Collection
Specimen Type
Collection
Requirements for Specimen Selection
- To ensure clinically relevant results, the most recent and/or metastatic sample is preferred to older specimens, provided sufficient tumor is present (see point 2).
- To ensure detection of all types of mutations there should be at least 10% tumor cells in the tissue area processed for DNA for mutation detection and 20% tumor cells for microsatellite instability evaluation. If there is more than one tissue block, please provide the block that has the greatest percentage of neoplastic nuclei.
- Tissue samples and pathology reports will be reviewed by directors upon receipt for acceptability prior to testing. Director consultation for tissue selection is available if needed (contact Genetics lab).
Specimen Types
Tissue samples
Send one of the following:
- Slides: 1 slide at 4-micron thickness stained with hematoxylin-and-eosin (H&E) AND 10 unstained, non-baked slides at 10-micron thickness (a minimum of 5 unstained slides is acceptable). Unstained slides can be on charged or uncharged slides.
- Tissue Blocks: Provide complete formalin-fixed tissue block containing tumor tissue. Tissue block will be returned at completion of testing.
- Fresh/frozen tissue: 5 microgram tissue in cell culture medium or frozen tissue stored at -20C. Tumor percentage will not be determined prior to sequencing studies.
NOTE: In order to ensure that enough DNA is obtained, the minimum acceptable tissue area is 10 square millimeters when ten 10-micron slides are supplied (1 cubic millimeter of tissue).
Purified DNA
5 micrograms ANDa reference hematoxylin-and-eosin (H&E) stained slide and pathology report required.
Bone Marrow
1 to 2 mL Bone Marrow in LAVENDER TOP (EDTA) tube
Blood
6 mL blood in LAVENDER TOP (EDTA) tube.
Alternative specimens may be acceptable with approval (contact: 206-598-1149).
For ADD-ON after prior testing, contact Genetics lab.
Unacceptable samples
We cannot accept decalcified samples or tissue samples treated with fixatives other than formalin.
Quantity:
Requested:
- Tissue: 10 unstained slides (10-micron thickness) plus one H&E-stained slide.
- Extracted DNA: 5 microgram Bone Marrow: 2 mL
- Blood: 6 mL
Minimum:
- Tissue: 5 unstained slides (10-micron thickness) plus one H&E-stained slide.
- Extracted DNA: 100-250 nanograms Bone Marrow: 1 mL
- Blood: 3 mL
Forms & Requisitions
Providers with access to the UW implementation of Epic (i.e., FHCC, HMC, SCCA, UWMC, UWNW) may order this test using the order "UW Genetics and Solid Tumor Test Request." See tip sheet for more information (internal link).
Handling Instructions
Attach a copy of the pathology report for the tumor sample being submitted.
Outside Laboratories: Ship at room temperature. Stability: unstained slides or tissue blocks stable at room temperature for at least 2 years.
Quantity
requested: Amounts as noted above
minimum: Amounts as noted above
Processing
Performance
LIS Dept Code
Genetics (GEN)
Performing Location(s)
| UW-MT |
Genetics
Attention: Genetics Lab Tel: 206-598–6429 M–F (7:30 AM–4:00 PM) Tel (EXOME only): 206-543-0459 |
Faculty |
|---|
Frequency
Run at least once a week; Typical Turnaround: 3 weeks *Turn around times may vary based on factors such as tissue acquisition and insurance preauthorization.
Available STAT?
No
Billing & Coding
CPT codes
81301
Billing Comments
For pricing information, contact Client Support Services 206-520-4600 or 800-713-5198.
LOINC
Interfaced Order Code
UOW2206