This is the first study performed in Murcia (south-eastern Spain) in which 592 families with hereditary breast and ovarian cancer were identified thanks to Genetic Counselling Units from this area over 6 years. Diagnostic performance was 18.1% and 194 different genetic variants were obtained. Variants with uncertain significance accounted for only 5.6% of the total number of reports, so our population has been well characterised. In BRCA1 gene, two novel variants were found (c.1859delT and c.3205C > T) and the most frequently detected mutations were c.68_69delAG, c.212 + 1G > A, c.5123C > A, c.211A > G and c.1918C > T, which together represented 56.67% of total pathogenic mutations. In BRCA2 gene, four recurrent variants were described (deletion of entire exon 2, c.9117G > A, c.3264dupT and c.3455T > G) representing 43.5% of the mutations in this gene. Mutation c.68_69delAG and deletion of entire exon 2 in BRCA1 and BRCA2 genes respectively were the most prevalent variants in our population. Regarding the genotype-phenotype relation, mutation c.212 + 1G > A appeared in an important percentage of breast and ovarian cancer cases, c.5123C > A in bilateral breast cancer and c.9117G > A in bilateral breast cancer and ovarian cancer. With respect to clinical-pathological characteristic, BRCA1/BRCA2 mutation carriers showed earlier onset age of breast tumour and higher risk of developing contra lateral breast cancer than non-informative cases. Moreover, association between either molecular subtype triple negative breast cancer or ovarian cancer and BRCA1 carriers was obtained.
Keywords: BRCA1; BRCA2; Genotype–phenotype relation; Hereditary breast and ovarian cancer (HBOC); Molecular subtype of breast cancer; Murcia population; Novel mutations; Prevalent mutations.