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.
Here, we investigated the contribution of BRCA1, BRCA2 and CHEK2 alterations to MBC predisposition in Italy by analysing a large series of MBC cases, unselected for breast cancer family history and all negative for BRCA1/BRCA2 germ-line mutations.
The relatives of bilateral cases who were wild-type for CHEK2 had three times the population risk of female breast cancer (145 cases: SIR 3.48 (95% CI 2.96-4.09), twice the risk of prostate cancer (34 cases: SIR 2.41, 1.67-3.36) and a large excess of male breast cancer (five cases: SIR 15.06, 4.92-35.36).
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.