The identification of individuals at-risk for hereditary breast cancer is important to ensure that appropriate risk reducing interventions are offered, to counsel patients and families regarding recurrence risk and to guide the decisions about cancer treatment interventions in affected individuals. The precise identification of at-risk individuals in a given family depends on the identification of a deleterious germline mutation in a cancer predisposition gene. In the case of the HBOC syndrome, genetic testing is often hampered by the complexity and cost of testing the BRCA genes, especially in lower resource countries. In Brazil, such testing is not yet covered by private insurance nor provided by the public health care system and its cost in private laboratories precludes its use for most at-risk families.
The initial screening of founder mutations in BRCA1 and BRCA2 before investigation of their entire coding regions has been well established in individuals of Ashkenazi Jewish ancestry as well as in a few other populations, and it is considered a cost-effective approach in these populations [25, 26]. In other Latin American communities, this issue has not been largely explored. An exception is a large cohort of Latin American HBOC families studied by Weitzel et al. (2005)  in which six recurrent mutations in BRCA1 accounted for 47% of the deleterious germline mutations and interestingly, the BRCA1 c.68_69del mutation, one of the Ashkenazi Jewish founder mutations, occurred in 3.6% of this clinic-based cohort of predominantly Mexican women. In this study the authors suggest that an initial diagnostic screen with a panel for these more commonly observed mutations could be cost-effective.
Only two reports from Brazilian breast-cancer affected patients have suggested that a founder BRCA1 mutation, c.5266dup, may be encountered at a significant prevalence [16, 17]. This mutation is the second most common mutation described in the Breast Cancer Information Core (BIC) database  for HBOC families worldwide. It has been reported in 14.0%, 10.0%, 6.0% and 4.0% of Ashkenazi Jewish, German, Italian and Russian women with breast cancer [29–32], respectively. It was also described in a recent study from Portugal, where it appeared in approximately 1.0% of the series studied . In addition, in a recent multi-national study, Hamel et al. (2011)  identified this mutation in several European countries. To our knowledge, it has not been detected in Spain [34, 35] nor in other South American countries, although only a few comprehensive mutation studies (i.e. including sequencing of the entire coding region of both genes and gene rearrangement testing) in HBOC families have been produced in these regions [34–40]. The penetrance of the BRCA1c.5266dup mutation has been well defined in Ashkenazi women, being associated with a cumulative lifetime risk of 0.67 for breast cancer and 0.33 for ovarian cancer .
In the present study, we screened 137 unrelated and self-referred non-Ashkenazi women at high risk for the HBOC syndrome for the three common founder mutations described in Ashkenazi Jewish cohorts and only BRCA1c.5266dup was identified, at a frequency of 5.0%. As expected, this frequency is higher than that described by the other Brazilian studies, including that of Gomes et al.  and Esteves et al , and likely results from the study design, that defined a significant personal and familial cancer history as inclusion criterion at recruitment.
Our results are in agreement with previous prevalence studies of the c.5266dup mutation in other high-risk non-Ashkenazi populations, such as the Italian and German populations [30, 31]. The origin of the BRCA1c.5266dup mutation in Brazilian patients and its relation to the Eastern-European counterpart remain to be determined. In a recently published study, da Costa et al. (2008)  evaluated the haplotypic profile of seven Brazilian carriers of c.5266dup and reported that all mutation carriers shared an identical haplotype, indicating a common origin. Some authors (i.e. Carvalho Silva et al.  and Gomes et al. ) have postulated that the entry of this mutation into Brazil is related to immigration of European Jews from Portugal in the sixteenth century. In the report by Weitzel et al. (2005) , that identified the Ashkenazi founder mutation c.68_69del in Mexican HBOC families, all mutation carriers shared the Ashkenazi Jewish founder haplotype. The authors postulate that Mexican carriers of these mutations are likely descendants of Conversos who immigrated to the Americas in the 15th-16th centuries and over generations assimilated into the larger Hispanic society. The same reasoning may be applied to the occurrence of BRCA1c.5266dup in Brazil. However, the absence of this mutation in studies from Spain or from other South American countries and the fact that only one case was reported in Portugal is against this hypothesis. Recent results from the study of Hamel et al. (2011) , show that the mutation probably originated in Scandinavia or Northern Russia, was then disseminated in European populations and thus could have entered Brazil through one or more of the several large European immigration waves in the 18th and 19th centuries. A detailed understanding of its entrance and distribution in Brazil, remains to be determined [45, 46].
One interesting finding of our study is the high frequency of the c.5266dup mutation in patients with bilateral breast cancer, compared to those with unilateral breast cancer. It is known that women with bilateral breast cancer are more likely to carry a BRCA mutation [47, 48]. Gershoni-Baruch et al. (1999) , studying Jewish women with bilateral breast cancer, found a high prevalence of founder mutations (31.0%), and 3.7% of the cases carried the c.5266dup mutation. In their report, bilateral breast cancer per se did not seem to reflect genetic predisposition unless associated with early age of onset. In another study that compared mutation prevalence in women with unilateral, family history positive and early onset breast cancer and women with bilateral breast cancer, the distribution of BRCA1c.5266dup was not significantly different between groups .
A limitation of our study is that we have not investigated the potential existence of other founder mutations that could become apparent after gene full gene sequencing; however, there is currently no published evidence for Brazilian BRCA founder mutations other than c.5266dup. We did not consider testing for founders described in Hispanic populations (i.e. Weitzel et al. (2005) ; Rodriguez et al. (2008) ) since it is our understanding that the population from the Brazilian cities studied here show trihybrid ancestries that are distinct from the Central American populations as indicated by studies from Alves-Silva et al. (2000)  and Parra et al. (2003) . Additionally, it has been demonstrated clearly that even mestizos from different Central and South American regions have significant intra- and interethnic variability and admixture profiles .
Finally, a debatable point regarding founder mutation frequency in a given population or high risk group, is how much is enough to justify screening. Although the economic analysis of such a question is beyond the scope of our study, there must be also a concern with the social and medical consequences of such testing. Given current knowledge, if a recommendation for screening of founder BRCA mutations is made for Brazilian HBOC women without subsequent comprehensive testing, most (likely > 90%) of the mutations carriers would remain unidentified. Such a recommendation could be erroneously interpreted as sufficient, or result in false tranquilization whenever negative, hampering continuation towards mutation testing of the entire coding region of both genes, which could obviously have serious consequences for these individuals and their families. This concern is further justified by the inaccessibility to proper cancer genetic counseling for most high-risk Brazilian women, and by the lack of coverage through both private and public health-based insurance of germline mutation testing. Thus, although the frequency of one single mutation, BRCA1c.5266dup is significant in this subset of Brazilian women with a personal and familial history of HBOC, initial screening for one founder mutation in at-risk patients should be performed in the setting of genetic counseling and within a cancer risk evaluation program. In a high-risk patient or family, testing should always include a comprehensive approach (full gene sequencing and rearrangement testing for both BRCA genes) when the initial founder mutation screening is negative.
We conclude that initial screening of the BRCA1 c.5266dup mutation in Brazilian individuals at high risk for HBOC is justified, but should be considered with caution. This statement is based on the frequency of the single founder mutation currently described in this population, lack of evidence of other founder BRCA mutants at a significant frequency in Brazil, and potential consequences of misinterpretation of negative screening results. These principles may apply to other highly admixed populations in South America and other continents.
It is imperative to concentrate efforts in making BRCA mutation testing and genetic counseling available to all high-risk patients in Brazil, and in educating health care professionals in the identification and proper management of these individuals. The best strategy for mutation screening and molecular diagnosis of high risk HBOC families in Brazil will only be fully understood after a comprehensive knowledge of BRCA mutation types and frequencies in this population.
Finally, the fact that two of the seven mutation-positive individuals had a limited family structure reinforce the importance of recognizing this feature and demonstrate that criteria for genetic testing must be adapted to consider this variable. The increased frequency of BRCA1c.5266dup in women with bilateral breast cancer should be further assessed in a larger cohort.