The majority of breast cancers are "sporadic," developing in patients with no associated hereditary mutations. On the other hand, hereditary cancer susceptibility gene mutations, the most common being BRCA1, occur in about 5-10% of patients with breast cancer. Of those women found to have the BRCA1 mutation who develop breast cancer, the vast majority -- 60-80% -- will have triple-negative breast cancer (TNBC), noted Roberto A. Leon-Ferre, MD, of the Mayo Clinic in Rochester, Minnesota.

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