A mosaic pathogenic variant in MSH6 causes MSH6-deficient colorectal and endometrial cancer in a patient classified as suspected Lynch syndrome: a case report.
Romy Walker, Mark Clendenning, Jihoon E Joo, Jessie Xue, Khalid Mahmood, Peter Georgeson, Julia Como, Sharelle Joseland, Susan G Preston, James M Chan, Mark A Jenkins, Christophe Rosty, Finlay A Macrae, Stephanie Di Palma, Ainsley Campbell, Ingrid M Winship, Daniel D Buchanan
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引用次数: 0
Abstract
Germline pathogenic variants in the DNA mismatch repair (MMR) genes (Lynch syndrome) predispose to colorectal (CRC) and endometrial (EC) cancer. However, mosaic variants in the MMR genes have been rarely described. We identified a likely de novo mosaic MSH6:c.1135_1139del p.Arg379* pathogenic variant in a patient diagnosed with suspected Lynch syndrome/Lynch-like syndrome. The patient developed MSH6-deficient EC and CRC at 54 and 58 years of age, respectively, without a detectable germline MMR pathogenic variant. Multigene panel sequencing of tumor and blood-derived DNA identified an MSH6 somatic mutation (MSH6:c.1135_1139del p.Arg379*) common to both the EC and CRC, raising suspicion of mosaicism. A droplet digital polymerase chain reaction (ddPCR) assay detected the MSH6 variant at 5.34% frequency in normal colonic tissue, 3.49% in saliva and 1.64% in blood DNA, demonstrating the presence of the MSH6 variant in all three germ layers. This study highlights the utility of tumor sequencing to guide sensitive ddPCR testing to detect low-level mosaicism in the MMR genes. Further investigation of the prevalence of MMR mosaicism is needed to inform routine diagnostic approaches and genetic counselling.
期刊介绍:
In recent years clinical cancer genetics has become increasingly important. Several events, in particular the developments in DNA-based technology, have contributed to this evolution. Clinical cancer genetics has now matured to a medical discipline which is truly multidisciplinary in which clinical and molecular geneticists work together with clinical and medical oncologists as well as with psycho-social workers.
Due to the multidisciplinary nature of clinical cancer genetics most papers are currently being published in a wide variety of journals on epidemiology, oncology and genetics. Familial Cancer provides a forum bringing these topics together focusing on the interests and needs of the clinician.
The journal mainly concentrates on clinical cancer genetics. Most major areas in the field shall be included, such as epidemiology of familial cancer, molecular analysis and diagnosis, clinical expression, treatment and prevention, counselling and the health economics of familial cancer.