BRCA2 is a gene that increases the risk of getting breast and ovarian cancer in women and breast and prostate cancer in men. Out of every 100 women who have a faulty version of this gene, between 80 and 85 will develop breast cancer at some point in their life (80 to 85% lifetime risk). Ovarian cancer lifetime risk is about 27%. Male carriers have an increased risk of breast cancer and prostate cancer.
Definition from Cancer Research UK: BRCA2