Stains & molecular markers
Microsatellite instability

Topic Completed: 1 June 2005

Minor changes: 23 December 2020

Copyright: 2002-2021,, Inc.

PubMed Search: Microsatellite instability [title]

Nat Pernick, M.D.
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Table of Contents
Definition / general
Cite this page: Pernick N. Microsatellite instability. website. Accessed January 20th, 2021.
Definition / general
  • Changes at (CA)n and (GT)n repeats, associated with dysfunction of DNA repair mechanisms
  • Involve MLH1, MSH2 proteins
  • Associated with all cases of hereditary nonpolyposis colorectal cancer and 15% of sporadic colorectal cancers
  • Hallmark of hereditary nonpolyposis colon cancer (HNPCC) associated tumors is defective mismatch repair, reflected in tumor tissue as microsatellite instability and loss of mismatch repair proteins MLH1, MSH2, MSH6, PMS2
  • Mismatch repair defects found in 15% of sporadic colorectal cancer in > 90% of HNPCC associated cancers
  • Defects present in 65% of adenomas from HNPCC patients
    • Loss of staining in patient suspected of having HNPCC may be used to direct mutation analysis (Mod Pathol 2005;18:1095)
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