Sign in →

Test Code TMSI Microsatellite Instability, Tumor


Necessary Information


A pathology report (final or preliminary), at minimum containing the following information, must accompany specimen for testing to be performed:

1. Patient name

2. Block number-must be on all blocks, slides, and paperwork (can be handwritten on the paperwork)

3. Tissue collection date

4. Source of the tissue



Specimen Required


This assay requires at least 40% tumor nuclei for endometrial specimens and at least 20% tumor nuclei for colorectal specimens.

-Preferred amount of tumor area with sufficient percent tumor nuclei: tissue 72 mm(2)

-Minimum amount of tumor area: 18 mm(2)

-These amounts are cumulative over up to 10 unstained slides and must have adequate percent tumor nuclei.

-Tissue fixation: formalin-fixed paraffin-embedded, non-decalcified

 

Preferred: Submit 2, if available, of the following specimens.

Acceptable: Submit at least one of the following specimens.

 

Specimen Type: Tissue block

Collection Instructions: Submit a formalin-fixed, paraffin-embedded tissue block with acceptable amount of tumor tissue.

 

Specimen Type: Tissue slide

Slides: 1 Hematoxylin and eosin-stained and 10 unstained

Collection Instructions:

Submit the followings slides:

1 Slide stained with hematoxylin and eosin

AND

10 Unstained, nonbaked slides with 5-micron thick sections of the tumor tissue.

Note: The total amount of required tumor nuclei can be obtained by scraping up to 10 slides from the same block.

Additional Information: Unused unstained slides will not be returned.

 


Forms

1. Molecular Genetics: Inherited Cancer Syndromes Patient Information (T519)

2. If not ordering electronically, complete, print, and send 1 of the following forms with the specimen:

-Gastroenterology and Hepatology Test Request (T728)

-Oncology Test Request (T729)

Useful For

Evaluation of tumor tissue to identify patients at high risk for having Lynch syndrome, also known as hereditary nonpolyposis colorectal cancer

 

Evaluation of tumor tissue for clinical decision-making purposes given the prognostic and therapeutic implications associated with microsatellite instability phenotypes

Disease States

  • Lynch syndrome

Method Name

Polymerase Chain Reaction (PCR)

Reporting Name

Tumor, Microsatellite Instability

Specimen Type

Varies

Specimen Stability Information

Specimen Type Temperature Time
Varies Ambient (preferred)
  Frozen 
  Refrigerated 

Reject Due To

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Clinical Information

Somatic (tumor-specific) microsatellite instability (MSI) is assessed by this test. MSI is characterized by numerous alterations in a type of repetitive DNA called microsatellites and occurs as the result of an impaired DNA mismatch repair process. Impaired DNA mismatch repair is a key factor in tumorigenesis and can occur sporadically or as the result of a hereditary cancer predisposition called Lynch syndrome.

 

Evaluation for MSI may be valuable for clinical decision making. Current data suggest that advanced stage solid tumors with defective DNA mismatch repair (MSI-high: MSI-H) are more likely to respond to treatment with immunotherapies, such as anti-PD-1 therapies. Colon cancers that demonstrate defective DNA mismatch repair (MSI-H) have a significantly better prognosis compared to those with intact mismatch repair (microsatellite stable/MSI- low: MSS/MSI-L). Additionally, current data indicate that stage II and stage III patients with colon cancers characterized by the presence of defective mismatch repair (MSI-H) may not benefit from treatment with fluorouracil alone or in combination with leucovorin. These findings are most likely to impact the management of patients with stage II disease.

 

Microsatellite instability analysis, usually in combination with immunohistochemistry staining of the mismatch repair proteins, can also provide helpful diagnostic information in the context of evaluation for Lynch syndrome. See Lynch Syndrome Testing Algorithm.

Reference Values

An interpretive report will be provided.

Day(s) Performed

Varies

Report Available

4 to 7 days

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

81301

88381-Microdissection, manual

Specimen Minimum Volume

See Specimen Required