Microsatellite instability

Author: Nat Pernick, M.D. (see Authors page)

Revised: 10 November 2015, last major update June 2005

Copyright: (c) 2002-2015,, Inc.

PubMed Search: Microsatellite instability [title]

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)
Micro Images
Missing Image

Loss of immunostaining