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Microsatellite Instability (MSI)

Reference Number: AA-00313

SECTION EIGHT

Dahl-Chase Diagnostic Services

MOLECULAR PATHOLOGY TESTING

MICROSATELLITE INSTABILITY (MSI) ANALYSIS

 

Clinical Significance:

 

Our laboratory performs PCR to assess the Microsatellite Instability (MSI) status on most newly diagnosed colorectal carcinomas.  MSI-H tumors are reflexed to MMR ICH testing and BRAF V600E mutation.  Since this mutation only rarely occurs in Lynch syndrome, its presence helps to identify sporadic (non-germline) MSI-H. 

 

 

Specimen Requirements and Collection:

Formalin fixed tissue containing a sufficient amount of tumor (generally at least several mm of tumor tissue submitted in the tissue block).  The MSI assay utilized by our laboratory will detect mutations as long as they constitute at least 10% of the DNA sample mix.

 

Forms:

Molecular Pathology requisition form

 

Transport:

Send paraffin block containing tumor at room temperature along with a normal tissue sample for allelic comparison

 

Reference Range:

Microsatellite Stable (MSS) = none of the 5 microsatellite markers unstable

High Microsatellite instability (MSI-H) = >/= 2 of 5 microsatellite markers unstable

Low Microsatellite instability (MSI-L) = 1 of 5 microsatellite markers unstable

 

 

CPT codes:

88381, 81301, G0452

 

 

 

Test reported:

Results are reported within 7-10 days