Mutation Patterns in Portuguese Families with Hereditary Breast and Ovarian Cancer Syndrome.

Germline pathogenic variants in the Breast Cancer Genes 1 () and 2 () are responsible for Hereditary Breast and Ovarian Cancer (HBOC) syndrome. Genetic susceptibility to breast cancer accounts for 5-10% of all cases, phenotypically presenting with characteristics such as an autosomal dominant inheritance pattern, earlier age of onset, bilateral tumours, male breast cancer, and ovarian tumours, among others. pathogenic variant is usually associated with other cancers such as melanoma, prostate, and pancreatic cancers. Many rearrangements of different mutations were found in both genes, with some ethnic groups having higher frequencies of specific mutations due to founder effects. Despite the heterogeneity of germline mutations in Portuguese breast or/and ovarian cancer families, the first described founder mutation in the gene (c.156_157insAlu) and two other variants in the gene (c.3331_3334del and c.2037delinsCC) contribute to about 50% of all pathogenic mutations. Furthermore, the families with the c.3331_3334del or the c.2037delinsCC mutations share a common haplotype, suggesting that these may also be founder mutations in the Portuguese population. Identifying specific and recurrent/founder mutations plays an important role in increasing the efficiency of genetic testing since it allows the use of more specific, cheaper and faster strategies to screen HBOC families. Therefore, this review aims to describe the mutational rearrangements of founder mutations and evaluate their impact on the genetic testing criteria for HBOC families of Portuguese ancestry.