Microsatellite instability is a test to determine genomic instability in colorectal cancer patients.
It is a well-established marker associated with Lynch syndrome and is also used to make therapy decisions in CRC patients.
Genetics - Molecular Oncology
FFPET: 6x 5-micron unstained FFPET slides (non-adhesive/uncharged preferred) PLUS 1x H&E stained slide with the tumour area marked (minimum 20% tumour content is required).
The Idylla MSI Test detects a novel panel of seven monomorphic biomarkers.
Each biomarker is scored for mutation status and results are combined for an overall sample microsatellite instability status as follows:
Microsatellite Stable (MSS) – 0 or 1 biomarkers with a ‘Mutation detected’ call
Microsatellite Instability High (MSI-H) – 2 or more biomarkers with a ‘Mutation detected’ call
Invalid Result – 3 or more biomarkers with an ‘Invalid’ call
The Idylla MSI Test has a Limit of Detection (LOD) of 10% mutant alleles in MSI-H samples.
Samples with <10% mutant alleles are below the LOD, and may not be identified as MSI-H.
The presence of microsatellite instability is consistent with the loss of expression of MLH1 and PMS2 by immunohistochemistry.
In the context of a family history suggestive of Hereditary Non-polyposis Colorectal Cancer, it is an indication for genetic analysis of one or more mismatch repair genes.
Such analysis is not indicated if the sample is microsatellite stable.
The Idylla MSI test is used.