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Original research
Microsatellite instability evaluation: which test to use for endometrial cancer?
  1. Paola Rafaniello-Raviele1,
  2. Ilaria Betella2,
  3. Alessandra Rappa1,
  4. Davide Vacirca1,
  5. Gianluca Tolva3,
  6. Aliana Guerrieri-Gonzaga3,
  7. Lucio Bertario3,
  8. Massimo Barberis1,
  9. Bernardo Bonanni3,
  10. Monica Marabelli3
  1. 1Division of Pathology, IEO, European Institute of Oncology IRCCS, Milan, Lombardy, Italy
  2. 2Department of Gynecologic Oncology, IEO, European Institute of Oncology IRCCS, Milan, Lombardy, Italy
  3. 3Division of Cancer Prevention and Genetics, IEO, European Institute of Oncology IRCCS, Milan, Lombardy, Italy
  1. Correspondence to Professor Massimo Barberis, Division of Pathology, IEO, European Institute of Oncology IRCCS, Milan, Lombardy, Italy; Massimo.Barberis{at}ieo.it

Abstract

Aims Analysis of microsatellite instability (MSI) is strongly recommended in endometrial cancer (EC) and colorectal cancer to screen for Lynch syndrome, to predict prognosis and to determine optimal treatment and follow-up. In a large monoinstitutional series of ECs, we evaluated the reliability and accuracy of Idylla assay, a rapid, fully automated system to detect MSI, and we compared its performance with two routine reference methods.

Methods We evaluated MSI status in 174 formalin-fixed, paraffin-embedded EC tissue samples using immunohistochemistry (IHC) for mismatch repair (MMR) proteins and Idylla assay. Samples with discordant or equivocal results were analysed with a third technique, the Promega MSI kit.

Results Idylla MSI assay and IHC were highly concordant (overall agreement: 154/170=90.59%, 95% CI 85.26% to 94.12%). However, in four samples, MMR-IHC staining was equivocal; moreover, 16 cases showed discordant results, that is, MMR deficient using IHC and microsatellite stable using Idylla. These 20 samples were reanalysed using the MSI-Promega kit, which showed the same results of Idylla assay in 18/20 cases (overall agreement: 90%, 95% CI 69.90% to 97.21%).

Conclusions Our results suggest that IHC is an efficient method to determine MMR status in ECs. However, the Idylla MSI assay is a rapid and reliable tool to define MSI status, and it could represent a valuable alternative to conventional MSI-PCR methods.

  • endometrium
  • carcinoma
  • diagnostic techniques and procedures
  • biomarkers
  • tumor
  • molecular biology

Data availability statement

All data relevant to the study are included in the article.

https://doi.org/10.1136/jclinpath-2021-207723

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    Data availability statement

    All data relevant to the study are included in the article.

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    Footnotes

    • Handling editor Runjan Chetty.

    • Twitter @IBetella

    • Contributors LB, MB and BB conceived the study. PR-R and IB collected samples and clinical data. AR, DV, P-RR and MB performed the experimental work. MM completed statistical analysis. MB supervised the experimental work. PR-R and MM wrote the manuscript. GT and AG-G reviewed and edited the manuscript. All the authors reviewed and edited the article and approved the final version of the manuscript.

    • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

    • Competing interests None declared.

    • Provenance and peer review Not commissioned; externally peer reviewed.