The diagnosis of hereditary cancer syndromes with atypical manifestation: clinical cases

Background: Germinal pathogenic variants are the cause of the development of hereditary cancer syndromes (HCS). Various genetic tests are used for HCS detect, from the «frequent» mutations of one or several genes analysis to the full-length gene sequence, next-generation sequencing (NGS) based panel, whole exome (WES) or whole genome sequencing (WGS).
There are some HCS cases with atypical clinical manifestations and the family history does not allow one to suspect a specific HCS and limit oneself to the study of only one or a few genes. Conducting research using NGS to assess the selected sample of cancer patient’s genetic characteristics has revealed atypical HCS cases.
Aim: To present the WGS diagnosis results for two atypical hereditary tumor syndromes cases.
Materials and methods: DNA isolation was performed using Qiagen DNA Isolation kit. WGS for all samples was performed at DNBSEQ-T7 (MGI) and DNBSEQ-G400 (MGI) sequencing platforms using PCR-free protocol with average sample coverage 30x. A standard bioinformatics analysis pipeline was implemented for all the samples data processing.
Potential clinically relevant variants were validated using Sanger sequencing. For all patients was received signed a written consent.
Results: In the first case report, a pathogenic variant in the TP53 gene was identified: c. 637C > T, p. Arg213Ter, rs397516436, and Li – Fraumeni syndrome was confirmed. In the second case, we detected two pathogenic variants carrier — BRCA2: c. 6644_6647del, p. Tyr2215SerfsTer13, rs80359616 and MSH2: c. 1906G > C, p. Ala636Pro, rs63750875 associated with hereditary breast and ovarian cancer and hereditary colorectal cancer (Lynch syndrome).
Conclusion: NGS, including WGS makes it easier to identify all clinically significant germline variants associated with hereditary cancer syndromes in cancer patients, as well as to trace their segregation in relatives.

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