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Validation of long mononucleotide repeat markers for microsatellite instability testing in paediatric tumours
  1. Chik Hong Kuick1,
  2. Wan Wan Chen2,
  3. Huiyi Chen1,
  4. Kenneth Tou En Chang1,3,
  5. Yingting Mok1,4
  1. 1 Department of Pathology and Laboratory Medicine, KK Women's and Children's Hospital, Singapore
  2. 2 Department of Pathology, Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China
  3. 3 Pathology Academic Clinical Programme, SingHealth Duke-NUS Medical School, Singapore
  4. 4 Department of Pathology, National University Health System, Singapore
  1. Correspondence to Dr Kenneth Tou En Chang, Department of Pathology and Laboratory Medicine, KK Women's and Children's Hospital, Singapore, Singapore; kenneth.chang.t.e{at}

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PD-1 inhibitors are a recent class of cancer drugs that have delivered promising results on some tumours that are refractory to standard treatment.1 Multiple biomarkers for response to anti PD-1 therapy have been proposed, of which microsatellite instability (MSI) has performed relatively well.2 A variety of MSI detection methods are available, of which fluorescent multiplex PCR of five mononucleotide repeat loci followed by capillary electrophoresis is a method that is used in several laboratories.3 More recently, the addition of long mononucleotide repeat (LMR) markers has been shown to increase the sensitivity of MSI-high (MSI-H) detection in colorectal and other cancer types.4 5

While MSI is well-studied in adult cancers, the literature on MSI in childhood cancers is more limited. In this study, we sought to survey the presence of MSI in a wide spectrum of paediatric solid tumours. In addition, we evaluated the utility of additional LMR markers in increasing the sensitivity of MSI detection in paediatric cancers.

Cases of refractory and aggressive paediatric solid tumours from 2011 to 2019 were retrieved from the archives of department of pathology and laboratory medicine, KK Women’s and Children’s Hospital. A total of 109 cases were selected for MSI testing, ensuring representation of common paediatric cancers as well as different organ systems. The study cohort included bone and soft tissue tumours (n=32), lymphomas (n=14), central nervous system tumours (n=13), germ cell tumours (n=13), neuroblastic tumours (n=7), retinoblastomas (n=5), Wilms tumour (n=4), adrenal cortical carcinoma (n=4), thyroid carcinoma (n=4), hepatoblastoma (n=3), pleuropulmonary …

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  • Handling editor Yoh Zen.

  • CHK and WWC contributed equally.

  • Contributors CHK, HYC and KTEC designed the study. HYC performed testing. WWC, CHK and YM performed data analysis and interpretation. CHK, YM and KTEC wrote the manuscript.

  • Funding This study was supported by Promega via the Promega Clinical Research Program.

  • Competing interests None declared.

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