RESUMO
Breast cancer is rare in male patients. Certain predisposing factors, be they genetic (e.g., BRCA2 gene mutations) or hormonal (imbalance between estrogen and androgen levels), have been implicated in male breast cancer pathophysiology. Male-to-female (MtF) transsexualism is a condition that generally involves cross-sex hormone therapy. Anti-androgens and estrogens are used to mimic the female hormonal environment and induce the cross-sex secondary characteristics. In certain situations, the change in the hormonal milieu can be disadvantageous and favor the development of hormone-dependent pathologies, such as cancer. We report a case of a MtF transgender patient who developed breast cancer after 7 years of cross-sex hormonal therapy. The patient was found to be BRCA2 positive, and suffered recurrent disease. The patient was unaware of being a member of an established BRCA2 mutation-positive kindred. This represents the first case of a BRCA2 mutation predisposing to breast cancer in a MtF transgender patient.