Researchers at the Institute of Cancer Research in Surrey, UK have discovered CHEK2, a new breast cancer gene that is believed to be associated with 1% of all female breast cancer cases and 9% of all male breast cancer cases. The mutation in the gene, known as CHEK2, confers a twofold increase in breast cancer risk in women, who typically have about a 13% chance of developing cancer in their lifetime. The gene mutation carries a tenfold increase of a man's risk of breast cancer, a much rarer occurrence.
Source: Nature Genetics April 2002