In terms of hormone receptors, 80.5% (62/77) of patients with MBC were estrogen receptor positive, 75.3% (58/77) of patients were progesterone receptor positive, and only 6.5% (5/77) of patients were HER2 overexpressing.
To extend our knowledge on the role of CHEK2 in susceptibility to male breast cancer we have screened a series of 26 breast cancer cases with male representation for germline sequence variation in the CHEK2 gene.
BRCA2 carries a risk of breast cancer similar to that of BRCA1, but is associated with a lower risk of ovarian cancer and a higher risk of male breast cancer.
We have adjusted the model to include BRCA2, but the use of this version must await publication of penetrance data for BRCA2, including those for male breast cancer that are apparently associated with BRCA2 but not with BRCA1.
Not only the estrogen receptor (ER), but also other steroid hormone receptors, including the androgen receptor (AR) and progesterone receptor (PgR) are expressed in MBC.
We screened genomic DNA for mutations in BRCA1 and BRCA2 and used family history data from these cases to calculate the risk of breast cancer to female relatives of MBC cases.
To evaluate the potential contribution of mutations in the BRCA1 and BRCA2 genes to male breast cancer (MBC), we expanded a previous study to screen a total of 261 Israeli men diagnosed with breast carcinoma.
Moreover, an analysis of genes correlated to steroid receptors and ERBB2 suggested a prominent role for the androgen receptor in MBC with a minor relevance for progesterone receptor and ERBB2, although, similarly to FBC, a genomic amplification could be observed.
Similarly, in the two cases of male breast cancer in which AR gene mutations have been described, the mutations in the DNA binding domain of the receptor are alike.
Moreover, an analysis of genes correlated to steroid receptors and ERBB2 suggested a prominent role for the androgen receptor in MBC with a minor relevance for progesterone receptor and ERBB2, although, similarly to FBC, a genomic amplification could be observed.
Several susceptibility genes have been established for female breast cancer, of which mutations in BRCA1 and especially in BRCA2 are also known risk factors for male breast cancer (MBC).
Pathogenic variants in BRCA2 [odds ratio (OR) = 13.9; p = 1.92 × 10<sup>-16</sup>], CHEK2 (OR = 3.7; p = 6.24 × 10<sup>-24</sup>), and PALB2 (OR = 6.6, p = 0.01) were associated with significantly increased risks of MBC.
Forty one male breast cancer samples were studied, including one sample from a man with spinal and bulbar muscular atrophy (SBMA), which is caused by an AR CAG repeat expansion.
However, the clustering of early pancreatic cancer in families with two breast cancers under age 50 years, the aggregation of ovarian cancer in families with breast and ovarian cancers, and the increased incidence of early onset prostate cancer in families with male breast cancer seem to be due to other effects unrelated to BRCA1/2 mutations.