Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Breast Cancer ?
    ### Response:
    Breast cancer affects one in eight women during their lives. Breast cancer kills more women in the United States than any cancer except lung cancer. No one knows why some women get breast cancer, but there are a number of risk factors. Risks that you cannot change include       - Age - the chance of getting breast cancer rises as a woman gets older     - Genes - there are two genes, BRCA1 and BRCA2, that greatly increase the risk.
    