Detection of DNA mismatch repair (MMR) deficiencies by immunohistochemistry can effectively diagnose the microsatellite instability (MSI) phenotype in endometrial carcinomas

Gynecol Oncol. 2015 May;137(2):306-10. doi: 10.1016/j.ygyno.2015.01.541. Epub 2015 Jan 28.

Abstract

Background: A proportion of endometrial carcinomas (ECs) are associated with deficient DNA mismatch repair (MMR). These tumors are characterized by high levels of microsatellite instability (MSI). Identification of MSI is important in identifying women who should be tested for Lynch syndrome and identifying a phenotype that may have specific prognostic and predictive implications. Genomic characterization of ECs has shown that MSI tumors form a distinct subgroup. The two most common methodologies for MSI assessment have not been compared in EC.

Methods: Pentaplex mono and di-nucleotide PCR for MSI testing was compared to MMR IHC (presence/absence of MLH1, MSH2, MSH6, PMS2) in a cohort of patients with EC. Concordance, Kappa statistic, sensitivity, specificity, positive and negative predictive values were obtained on the cross-tabulation of results.

Results: Comparison of both MSI and MMR status was complete for 89 cases. Overall agreement between methods (concordance) was 93.3% (95% CI[85.9%-97.5%]). A one-sided test to determine whether the accuracy is better than the "no information rate," which is taken to be the largest class percentage in the data, is significant (p<0.00001). Unweighted Kappa was 0.84, along with the sensitivity (88.5%), specificity (95.2%), PPV (88.5%), and NPV (95.2%). The balanced accuracy (i.e. the average between sensitivity and specificity) was 92%.

Discussion: We show the equivalence of MSI testing and MMR IHC. We advocate the implementation of MMR IHC in future EC classification schemes, enabling stratification of cases for future clinical trials as well as assisting identification of Lynch syndrome, so that screening and risk reducing interventions can be undertaken.

Keywords: Endometrial cancer; Lynch syndrome; Microsatellite instability; Mismatch repair.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptor Proteins, Signal Transducing / genetics
  • Adenosine Triphosphatases / genetics
  • Biomarkers, Tumor / genetics
  • Cohort Studies
  • DNA Mismatch Repair*
  • DNA Repair Enzymes / genetics
  • DNA-Binding Proteins / genetics
  • Endometrial Neoplasms / genetics*
  • Endometrial Neoplasms / pathology
  • Female
  • Humans
  • Immunohistochemistry
  • Microsatellite Instability*
  • Middle Aged
  • Mismatch Repair Endonuclease PMS2
  • MutL Protein Homolog 1
  • MutS Homolog 2 Protein / genetics
  • Nuclear Proteins / genetics
  • Phenotype

Substances

  • Adaptor Proteins, Signal Transducing
  • Biomarkers, Tumor
  • DNA-Binding Proteins
  • G-T mismatch-binding protein
  • MLH1 protein, human
  • Nuclear Proteins
  • Adenosine Triphosphatases
  • PMS2 protein, human
  • MSH2 protein, human
  • Mismatch Repair Endonuclease PMS2
  • MutL Protein Homolog 1
  • MutS Homolog 2 Protein
  • DNA Repair Enzymes