Microsatellite Instability (MSI) and Mismatch Repair Protein Analysis
- Description
- MSI is a key factor in several cancers particularly GI tract and gynaecological malignancies. Two mechanisms have been proposed for MSI occurrence. The first is in hereditary non-polyposis colorectal cancer (HNPCC) or Lynch Syndrome, where an inherited mutation in a mismatch-repair (MMR) gene causes a microsatellite repeat replication error to go unfixed. The second mechanism is the result of an epigenetic change which silences an essential MMR gene. In both cases, microsatellite insertions and deletions within polymorphic DNA regions result in uncontrolled cell division and tumor growth. Expression of the MMR proteins involved, MSH2, MLH1, MSH6 and PMS2 can be detected by immunohistochemistry. No or low expression of one or more of these is indicative of MSI and should be further tested as below. Five markers have been recommended by the National Cancer Institute to screen for MSI in HNPCC tumors (often called Bethesda markers). Generally, MSI detection in >30% of the markers is considered to be MSI-high (MSI-H) whereas microsatellite abnormalities in <30% of the markers is considered MSI-low. Correlation between MMR protein expression and MSI is essential for patient management.
- Testing site
- Synnovis : Tissue Sciences : St Thomas' Hospital
- Laboratory
- Histology/ Histopathology
- Sample type and volume required
- Representative paraffin processed blocks of both tumour and normal tissue, ideally in separate blocks.
- Storage and transport
- First class post within 4 days (temperature not to exceed 30°C during transport)
- Turnaround time
- 2 - 3 weeks
- Contacts
Histopathology Laboratory at Blackfriars Hub
Phone: 020 4614 7519/ 7522
Friars Bridge Court,
41-43 Blackfriars Road,
London, SE1 8NZHistology Laboratory at Princess Royal University Hospital
Phone: 01689 864314
Princess Royal University Hospital
Farnborough Common
Orpington
Kent
BR6 8NDCellular Pathology/Histopathology at King’s College Hospital
Phone: 020 3299 3045
kch-tr.histopathologyoffice@nhs.net
King’s College Hospital
Bessemer Wing – 2nd Floor
Denmark Hill
London SE5 9RSCellular Pathology at St Thomas’ Hospital
Phone – Histology: 0207 188 7188 extension 54611
Phone – Cytology: 0207 188 2915
Phone – Oral Pathology: 0207 188 4367
Histopathology & Cytopathology Laboratories
Cellular Pathology
St Thomas’ Hospital
North Wing – 2nd Floor
Westminster Bridge Road
London SE1 7EHCellular Pathology at Guy’s Hospital
Head and Neck/Oral Pathology Laboratory
4th Floor, Tower Wing
Guy’s Hospital
Great Maze Pond
London SE1 9RT