RESUMO
The contribution of BRCA1 and BRCA2 tobreast cancer incidence in Brazil has not yet been explored. In order to estimate the proportion of breast cancers due to BRCA1 and BRCA2 mutations in Brazil,we conducted a study of unselected breast cancer patients from Rio de Janeiro, Brazil. We enrolled 402women with breast cancer from a large public hospital and two private medical clinics in the city. A detailed family history was obtained from each patient and a blood sample was obtained for DNA analysis. Mutations in BRCA1 and BRCA2 were sought using a combination of techniques, but all mutations wereconfirmed by direct sequencing. Overall, nine mutations were identified (six in BRCA1 and three in BRCA2)representing 2.3 percent of the total. The most common mutation, 5382insC in BRCA1, was seen five times andaccounted for 56 percent of all identified mutations. A second mutation, in BRCA2 (6633del5) was seen in two unrelatedwomen. In summary, BRCA1 and BRCA2mutations are not uncommon in Brazilian women with breast cancer. It appears that a small number of foundermutations may be predominant. Moreover, a small number of founder mutations may be prevalent inBrazil, raising the possibility that a rapid and inexpensivegenetic test may be developed to screen for inheritedsusceptibility to breast cancer in Brazil.