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
