Case Report
Copyright ©The Author(s) 2023. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Clin Cases. May 6, 2023; 11(13): 3105-3113
Published online May 6, 2023. doi: 10.12998/wjcc.v11.i13.3105
Discrepancy among microsatellite instability detection methodologies in non-colorectal cancer: Report of 3 cases
Elif Şenocak Taşçı, İbrahim Yıldız, Sibel Erdamar, Leyla Özer
Elif Şenocak Taşçı, İbrahim Yıldız, Leyla Özer, Department of Medical Oncology, Acıbadem MAA University, Istanbul 12345, Turkey
Sibel Erdamar, Department of Pathology, Acıbadem MAA University, Istanbul 12345, Turkey
Author contributions: Yıldız İ and Özer L designed research; Şenocak Taşçı E performed research; Erdamar S analyzed data; and Şenocak Taşçı E and Yıldız İ wrote the paper.
Informed consent statement: Informed written consent was obtained from the patients for publication of this report.
Conflict-of-interest statement: All authors report having no relevant conflicts of interest for this article.
CARE Checklist (2016) statement: The authors have read the CARE Checklist (2016), and the manuscript was prepared and revised according to the CARE Checklist (2016).
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: https://creativecommons.org/Licenses/by-nc/4.0/
Corresponding author: Leyla Özer, Doctor, MD, Associate Professor, Department of Medical Oncology, Acıbadem MAA University, Acibadem Mehmet Ali Aydinlar University Atakent Hospital, Turgut Ozal Bulvarı, No. 16, Halkalı, Istanbul 12345, Turkey. leyla.ozer@acibadem.com
Received: February 7, 2023
Peer-review started: February 7, 2023
First decision: February 28, 2023
Revised: March 16, 2023
Accepted: April 4, 2023
Article in press: April 4, 2023
Published online: May 6, 2023
Processing time: 76 Days and 14.6 Hours
Abstract
BACKGROUND

Microsatellite instability (MSI) is a predictive biomarker for cancer immunotherapy. The tumor-agnostic nature of MSI makes it a denominator for immunotherapy in several solid tumors. It can be assessed using next-generation sequencing (NGS), fluorescent multiplex PCR, and immunohistochemistry (IHC).

CASE SUMMARY

Here, we report 3 cases with discordant MSI results detected using different methods. A cholangiocellular carcinoma case revealed proficient mismatch repair (MMR) by IHC but high MSI (MSI-H) by liquid NGS. A cervical cancer case revealed deficient MMR by IHC, microsatellite stable by PCR, and MSI-H by NGS. Lastly, an endometrial cancer case revealed proficient MMR by IHC but MSI-H by NGS.

CONCLUSION

IHC for MMR status is the first choice due to several advantages. However, in cases of indeterminate IHC results, molecular testing by MSI-PCR is preferred. Recently, NGS-based MSI assays are being widely used to detect MSI-H tumors. All three methods have high accuracy; however, the inconsistencies between them may lead to misdiagnosis.

Keywords: Discordance; Immunohistochemistry; Microsatellite instability; Next-generation sequencing; Case report

Core Tip: Microsatellite instability (MSI), a predictive biomarker for cancer immunotherapy can be assessed using next-generation sequencing, fluorescent multiplex PCR, and immunohistochemistry (IHC). Even though IHC for mismatch repair status is the first choice, in cases of indeterminate IHC results, molecular testing by MSI-PCR is preferred. Recently, next-generation sequencing-based MSI assays are also being widely used. Although all methods have high accuracy, they may have inconsistent results leading to misdiagnosis.