Breast cancer BRCA1/2 testing is used to predict who is at risk of developing breast cancer and to determine if the breast cancer is hereditary. BRCA1/2, also known as breast cancer susceptibility gene 1 and breast cancer susceptibility gene 2, play a very important role in the pathogenesis of hereditary breast cancer. Both genes are oncogenes. Approximately 40-50% of patients with hereditary breast cancer have mutations in BRCA1. The remaining 50% of patients have BRCA2 mutations. Clinical studies have confirmed that the incidence of breast cancer in people with hereditary BRCA1/2 mutations is significantly higher than in the general population.