RESUMO
Estima-se que para o câncer de mama, assim como para grande parte dos tumores malignos conhecidos, 5 a 10% sejam de caráter hereditário. A história de câncer em familiares de primeiro grau e a presença de alguns fatores específicos de risco, como câncer de mama bilateral, história familiar de câncer de mama e ovário, e câncer de mama em indivíduo do sexo masculino, são indicadores importantes de risco de câncer de mama hereditário. Os avanços em técnicas de biologia molecular nas últimas décadas resultaram na identificação de genes que, quando alterados, aumentam significativamente o risco de desenvolver câncer de mama, de ovário e outros tumores. Destacam-se os genes supressores tumorais BRCA1 e BRCA2, além de outros genes de predisposição ao câncer de mama identificados, que são igualmente importantes no risco da doença, embora correspondam a uma parcela menor dos casos hereditários. A possibilidade de identificar pacientes e familiares com elevado risco de desenvolvimento de câncer torna possível o emprego de uma abordagem preventiva e de detecção precoce do câncer. Além disso, a identificação de um indivíduo não portador de uma alteração genética em uma família de risco permite a tranquilização dele e elimina gastos/complicações com intervenções preventivas desnecessárias. Famílias de alto risco de desenvolvimento de câncer hereditário apresentam alta prevalência de câncer de mama, além de neoplasia com instalação precoce e com maior agressividade. Dessa forma, o rastreamento nesses casos deve ser diferente, objetivando alcançar a redução da morbidade e mortalidade associadas ao câncer nessa população.
It is estimated that for breast cancer, as well as for the great majority of malignant tumors, 5 to 10% are due to an inherited predisposition. Family history of cancer in first degree relatives and the presence of some specific risk factors, such as bilateral breast cancer, family history of breast and ovarian cancer, and breast cancer in a male person, are important indicators of risk for hereditary breast cancer. Advances in molecular biology in recent decades have resulted in the identification of genes that, when altered, increase significantly the risk of developing breast cancer, ovarian cancer and other tumors, for example, the tumor suppressor genes BRCA1 and BRCA2, as well as other genes predisposing to breast cancer identified, which are equally important in the risk for the disease, although a smaller portion of match cases hereditary. The ability to identify patients and relatives with high risk for developing cancer makes possible the use of a preventive approach and an early detection of cancer. In addition, the identification of a non-carrier individual in a family of high risk allows him to reassures the modification individual and eliminates expenses/complications with unnecessary preventive interventions. The typical profile of a patient with higher risk is high prevalence of breast cancer, earlier ages at cancer diagnosis and the worst prognosis and evolution of the tumor. In this way, follow up for these patients must be different in order to achieve the reduction of morbidity and mortality associated with cancer in this population.
RESUMO
Women with mutations in the breast cancer genes BRCA1 or BRCA2 have an increased lifetime risk of developing breast, ovarian and other BRCA-associated cancers. However, the number of detected germline mutations in families with hereditary breast and ovarian cancer (HBOC) syndrome is lower than expected based upon genetic linkage data. Undetected deleterious mutations in the BRCA genes in some high-risk families are due to the presence of intragenic rearrangements such as deletions, duplications or insertions that span whole exons. This article reviews the molecular aspects of BRCA1 and BRCA2 rearrangements and their frequency among different populations. An overview of the techniques used to screen for large rearrangements in BRCA1 and BRCA2 is also presented. The detection of rearrangements in BRCA genes, especially BRCA1, offers a promising outlook for mutation screening in clinical practice, particularly in HBOC families that test negative for a germline mutation assessed by traditional methods.