Mutational analysis of BRCA1 and BRCA2 in Mediterranean Spanish women with early-onset breast cancer: identification of three novel pathogenic mutations.

In Spain, the contribution of BRCA mutations to the population incidence of early-onset breast cancer was unknown. We carried out a mutational analysis of the BRCA1 and BRCA2 genes in 124 Spanish women diagnosed with breast cancer before the age 41 and who were not selected for a family history of this disease. The genetic study was performed by PCR-SSCP analysis and DNA sequencing. We identified 6 pathogenic BRCA mutations in 7 unrelated probands (5.6%; 95% CI=2.3% to 11.3%): 1 BRCA1 (c.2080delA) and 5 BRCA2 (p.Y3006X, p.Q1994X, c.9204_9217del14, c.9254_9258del5 and c.295+2T>C). Three out of 6 mutations were novel (BRCA2 p.Y3006X, c.9204_9217del14, and c.295+2T>C), and two further mutations had not been previously found in Spain (BRCA1 c.2080delA and BRCA2 p.Q1994X). The one remaining (BRCA2 c.9254_9258del5) was detected in two probands of our sample. Additionally, we identified two new missense mutations: BRCA1 p.P1812A and BRCA2 p.G2044A. Our data support the notion that Spaniards represent a heterogeneous population with its own spectrum of BRCA mutations, some of which appear as founding mutations. We categorized patients into familial or non-familial groups on the basis of her family history of breast/ovarian cancer; this analysis indicated that among Spanish women with early-onset breast cancer, an even moderate family history is a good predictor of being a BRCA mutation carrier.