BRCA2 and breast cancer: Eleven percent to 40% of men with breast cancer carry this mutation.26 The highest known prevalence of BRCA2 mutations in male patients with breast cancer is in Iceland, where a founder mutation accounts for 40% of all cases.27 Little is known about the distinguishing characteristics of breast cancer in men with BRCA2 mutations, although men with a mutation may present with disease at an earlier age.28