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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

Testing Algorithm

When this test is ordered, slide review will always be performed at an additional charge.

 

For more information see Lynch Syndrome Testing Algorithm

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.

Reference Values

An interpretive report will be provided.

Supportive Data

A total of 100 accuracy samples were run retrospectively during verification; 55/100 samples were colorectal, 41/100 were endometrial, and the remaining 4/100 were other tumor types. The overall concordance between the Idylla and Promega results was 98/100 (98%). Seventy-nine of 100 samples were microsatellite stable (MSS) by Promega and 77 (97%) had concordant MSS results by Idylla. Twenty-one of 100 samples were microsatellite instability-high (MSI-H) by Promega and 21 (100%) had concordant MSI-H results by Idylla.

 

In addition to the retrospective samples, 100 consecutive samples were prospectively analyzed, of which 58 were colorectal, 31 were endometrial, and 11 were from other tumor types. Seventy-six of 100 samples were MSS by Promega and all (100%) were MSS by the Idylla assay. Twenty-four of 100 samples were MSI-H by Promega. Twenty-three of 24 (96%) of the MSI-H samples were concordant by Idylla. One patient had an uncommon reason for testing. The discordant sample DNA was rerun on the Promega platform, but there was not sufficient tissue remaining to rerun this specimen on the Idylla assay. After reviewing the results from the 2 runs on Promega, a consensus decision amongst 5 pathologists was reached, and the sample was reclassified as equivocal by the Promega assay.

 

Precision and reproducibility were evaluated by running 3 MSI-H samples and 3 MSS samples in triplicate on the same instrument. Each of these samples had a 4th cartridge run on a separate instrument. There was 100% concordance between replicates from the 3 MSI-H samples and 3 MSS samples.

Day(s) Performed

Varies

Report Available

4 to 7 days

Specimen Retention Time

Tissue blocks: Unused portions of blocks will be returned; Tissue slides: Unused slides are stored for at least 5 years; Extracted DNA: 3 months

Performing Laboratory

Mayo Clinic Laboratories in Rochester

CPT Code Information

81301

88381-Microdissection, manual

LOINC Code Information

Test ID Test Order Name Order LOINC Value
TMSI Tumor, Microsatellite Instability 81711-4

 

Result ID Test Result Name Result LOINC Value
609365 Result Summary 50397-9
609366 Result 43368-0
609367 Interpretation 69047-9
609368 Specimen 31208-2
609369 Source 31208-2
609370 Tissue ID 80398-1
609371 Released By 18771-6

Additional Tests

Test ID Reporting Name Available Separately Always Performed
SLIRV Slide Review in MG No, (Bill only) Yes

Specimen Minimum Volume

See Specimen Required