Genetic, Surgical and Oncological Approach to Breast Cancer, with BRCA1, BRCA2, CDH1, PALB2, PTEN and TP53 Variants.

Objective: The aim of this study was to determine the frequency of germline variants in BRCA1, BRCA2, CDH1, PALB2, PTEN and TP53 in patients admitted to a medical genetics clinic with breast cancer and to assess these identified variants according to published genetic, surgical and oncological perspectives. Materials and Methods: Medical history, and cancer diagnosis information for 195 independent probands with operated breast cancer were collected from requisition forms and medical records. The exonic regions and exon-intron junctions in BRCA1, BRCA2, CDH1, PALB2, PTEN and TP53 genes were sequenced. Analysis of fastq files was performed on the Qiagen Clinical Insight-Analyse Universal with panel-specific pipeline and vcf files were interpreted clinically using Qiagen Clinical Insight-Interpret. Results: Gene variants (pathogenic, likely pathogenic and variants of unknown significance) were detected in 53 (27.2%). Detailed information about the patients (age of diagnosis, family history, gender), cancer stage, tumour characteristics (ER, PR, human epidermal growth factor receptor 2 status) and all information related to the detected variants (gene, location, nucleotide and amino acid change, exon number, impact, mutation classification, dbSNP number and HGMD variant class) were assessed. In total, 58 mutations were identified including 14 novel, previously unreported variants. Conclusion: Molecular characterization and identification of mutations have important implications for predictive, preventive, and personalized medicine, including genetic counseling and development of specific treatment protocols. We emphasize variants of unknown significance (VUS) as the clinical significance of VUS changes over time and variant classification is important for clinical molecular genetic testing and clinical guidance. This study may provide new insights into risk assessment for variants in CDH1, PALB2, PTEN and TP53, in addition to BRCA1 and BRCA2, which may prove useful for clinical management of breast cancer patients. Further studies are needed to identify the common gene variants in the Turkish population and evaluate the pathogenity of VUS.