BRCA1 and breast cancer: Two other publications with projects conducted in the Mexican population reported relevant data regarding 9–12 del BRCA1. In the first study, which involved patients with breast and ovarian cancer, without suspicion of hereditary cancer, 9–12 del BRCA1 represented 33% of the total mutations identified, 35% in the subgroup of patients with ovarian cancer and 29% in that of patients with breast cancer, constituting the most frequent mutation [15].