Genetic Predisposition to Male Breast Cancer.

Male breast cancer (mBC) is a rare cancer diagnosis that constitutes less than 1 % of all breast cancer cases globally. Genetic factors play an important role in the mBC risk. Germline pathogenic variants (PVs) in cancer predisposition genes could be identified in about 15 % of cases. We performed germline genetic testing in 248 Czech mBC patients and 3,626 non-cancer male controls using next-generation sequencing by the CZECANCA panel (226 genes). We identified 46/248 (18.5 %) carriers of PVs in the established mBC predisposition genes, primarily in BRCA2 (N = 34), less frequently in BRCA1 (N = 7) and PALB2 (N = 5). The presence of a PV in these genes significantly increased the mBC risk (OR 44.04; 5.82; and 8.26, respectively). Additionally, we identified 16 carriers of PVs in candidate mBC genes, but only PVs in CHEK2 were significantly associated with increased mBC risk (OR = 4.98). The significance of 26 germline alterations in 23/192 additionally analysed genes remained uncertain. The carriers of PVs in BRCA1 and CHEK2 were significantly younger (55.8 and 52.6 years, respectively) than non-carriers (64.8 years), and all carriers of PVs in the established genes had more frequently grade G3 tumours and positive family cancer history. Our study underscores the critical role of BRCA2 in mBC predisposition while also highlighting the potential contributions of additional genes that warrant further investigation. Moreover, it supports and justifies universal genetic testing for all mBC patients to generally improve early cancer detection and tailored treatment.