Microsatellite Instability

General Information

Lab Name

Lab Code

MSI

Epic Ordering

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

Forms & Requisitions

Genetics Requisition

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).

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.

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

Guidelines

Ordering & Collection

Specimen Type

Tumor Tissue, Purified DNA, Bone Marrow, accompanied by a PATHOLOGY REPORT for the tested tissue.

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

Genetics Requisition

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

Processing

Performance

LIS Dept Code

Genetics (GEN)

Performing Location(s)

UW-MT	Genetics Attention: Genetics Lab Clinical lab, Room NW220 University of Washington Medical Center 1959 NE Pacific Street Seattle, WA 98195 Tel: 206-598–6429 M–F (7:30 AM–4:00 PM) Fax: 206-616-4584 Lab email: cgateam@uw.edu Tel (EXOME only): 206-543-0459	Faculty Jillian Buchan, PhD, FACMG Runjun Kumar, MD, PhD Regina Kwon, MD, MPH Christina Lockwood, PhD, DABCC, DABMGG Abbye McEwen, MD, PhD Colin Pritchard, MD, PhD Vera Paulson, MD, PhD Eric Konnick, MD, MS He Fang, PhD

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?

Billing & Coding

CPT codes: 81301
Billing Comments: For pricing information, contact Client Support Services 206-520-4600 or 800-713-5198.
LOINC: 43368-0
Interfaced Order Code: UOW2206