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pISSN 2384-2458 eISSN 2288-7261
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Case Report

J Lab Med Qual Assur 2019; 41(4): 220-224

Published online December 31, 2019

https://doi.org/10.15263/jlmqa.2019.41.4.220

Copyright © Korean Association of External Quality Assessment Service.

A Case of Lynch Syndrome with the Deletion of Multiple Exons of the MLH1 Gene, Detected by Next-Generation Sequencing

Jinyoung Hong1, Hyunki Kim1, Yong Sang Hong2, Woochang Lee1, Seok-Byung Lim3, Jeong-Sik Byeon4, Sail Chun1, and Won-Ki Min1

Departments of 1Laboratory Medicine, 2Oncology, 3Surgery, and 4Gastroenterology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea

Correspondence to:Woochang Lee
Department of Laboratory Medicine, Asan Medical Center, University of Ulsan College of Medicine, 88 Olympic-ro 43-gil, Songpa-gu, Seoul 05505, Korea
Tel: +82-2-3010-4506 Fax: +82-2-478-0884 E-mail: wlee1@amc.seoul.kr

Received: October 18, 2019; Revised: November 7, 2019; Accepted: November 9, 2019

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

A 26-year-old man underwent colonoscopy to investigate weight loss and a lesion suspi- cious of colorectal cancer was detected. He had a family history of colorectal cancer and hepatocellular carcinoma. The biopsy result of the lesion showed a well-differentiated adeno- carcinoma of the sigmoid colon and he underwent curative anterior resection of the colon. A microsatellite instability (MSI) test was performed on the resected tumor tissue specimen and it was found to be MSI-high. A next-generation sequencing (NGS)-based hereditary tumor panel test was performed on his peripheral blood to detect the causative germline variant. Neither a pathogenic variant nor a variant of uncertain significance was found in the single nucleotide variant (SNV) and small indel variant analyses. However, a copy number variation (CNV) detection algorithm identified a variant compatible with the deletion of exon 7 to exon 19 of the MLH1 gene. This finding was confirmed to be a true deletion by multiplex ligation-dependent probe amplification. Therefore, the deletion of exon 7 to exon 19 of the MLH1 gene was regarded as the causative pathogenic genetic variant for his colorectal cancer and familial genetic testing was recommended. Therefore, patients with suspected cancer syndromes, including hereditary colorectal cancer, should be tested for germline mutations including CNVs, SNVs, and indels. NGS is a technique that can simultaneously detect SNVs and CNVs and therefore, it has clinical utility for genetic testing for hereditary diseases.

Keywords: DNA copy number variation, MLH1, Next-generation sequencing

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