Genetic Landscape of Male Breast Cancer

Simple Summary Male breast cancer is a rare disease, representing around 0.5% of the malignances in men. Although they receive the same treatment as women with breast cancer, there is increasing knowledge showing that both have a distinct genetic background. Pathogenic variants in cancer predisposing genes are a likely etiology for male breast cancer in 4% to 40% of the cases, and it is currently recommended that all men diagnosed with breast cancer be offered genetic counseling followed by genetic testing. Even though, men are still less likely to undergo the test than women for many reasons, which include an unfamiliarity with the issue by health professionals. The purpose of this article is to review the current knowledge of the germline genetic background of male breast cancer and its impact in the management of the patients and their families. Male breast cancer (MBC) is now considered molecularly different from female breast cancer (FBC). Evidence from studies indicates that common genetic and epigenetic features of FBC are not shared with those diagnosed in men. Genetic predisposition is likely to play a significant role in the tumorigenesis of this rare disease. Inherited germline variants in BRCA1 and BRCA2 account for around 2% and 10% of MBC cases, respectively, and the lifetime risk of breast cancer for men harboring BRCA1 and BRCA2 mutations is 1.2% and 6.8%. As for FBC, pathogenic mutations in other breast cancer genes have also been recently associated with an increased risk of MBC, such as PALB2 and CHEK2 mutations. However, while multigene germline panels have been extensively performed for BC female patients, the rarity of MBC has resulted in limited data to allow the understanding of the magnitude of risk and the contribution of recently identified moderate penetrance genes of FBC for MBC predisposition. This review gathers available data about the germline genetic landscape of men affected by breast cancer, estimated risk associated with these genetic variants, and current guidelines for clinical management.