Microsatellite Instability
Also written as MSI.
Characterized by fewer polyps than FAP but an increased risk of colorectal and extracolonic cancers via the microsatellite instability pathway.
What our notes say
- Characterized by fewer polyps than FAP but an increased risk of colorectal and extracolonic cancers via the microsatellite instability pathway. (Gastrointestinal Neoplasms: High-Yield Exam Review)
- *Pathogenesis:* Adenoma-carcinoma sequence (APC, KRAS, p53 mutations); APC mutation typically initiating; further mutations drive invasion; alternative pathway via microsatellite instability (Lynch syndrome) (Medical MCQs: Chemical Pathology & Haematology Exam Review)
- Microsatellite instability pathway: MLH1/MSH2 defects → Lynch syndrome, right-sided, less polyp-dependent (Dr. Irungu Notes)
- Alternative pathway: Lynch syndrome/HNPCC follows the microsatellite instability pathway (mismatch repair gene mutations — MLH1, MSH2), distinct from the APC/chromosomal instability pathway above (Essential Cardiovascular Pathology: Atherosclerosis to Endoc)
- Examples: MLH1, MSH2 → microsatellite instability → hereditary non-polyposis colorectal cancer (HNPCC/Lynch syndrome) (Genetic Disorders Pathology Crash Course: Exam Revision Notes)
- | HNPCC (Lynch syndrome) | Mismatch repair (MMR) | Microsatellite instability (MSI) | Colorectal carcinoma | (Hallmarks of Cancer: Molecular Basis, Cell Cycle & Oncogenes)
Study material on Microsatellite Instability
- Gastropathology Pathology
- Gastrointestinal Neoplasms: High-Yield Exam Review
- Hallmarks of Cancer: Molecular Basis, Cell Cycle & Oncogenes
- ONCOPATHOLOGY - 30 KEY SHORT ANSWER QUESTIONS Hallmarks 1,2 & 3
- GASTROINTESTINAL PATHOLOGY (Part 2)
- Tumours of the Gastrointestinal Tract
- Gastropathology Pathology
- Gastropathology Pathology
- ONCOPATHOLOGY MCQ EXAMINATION HAllmarks of Cancer 1,2 &3
Practice questions on Microsatellite Instability
Why do cancer cells typically show microsatellite instability (MSI) in hereditary nonpolyposis colon cancer (HNPCC)?
- Enhanced DNA synthesis
- Defective mismatch repair system
- Overactive nucleotide excision repair
- Loss of telomerase activity
Answer: B. HNPCC patients have mutations in mismatch repair genes, leading to failure to correct replication errors, particularly in repetitive sequences (microsatellites), causing MSI. ---