Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Breast Cancer ?
    ### Response:
    Key Points
                    - Breast cancer is a disease in which malignant (cancer) cells form in the tissues of the breast.    -  A family history of breast cancer and other factors increase the risk of breast cancer.    - Breast cancer is sometimes caused by inherited gene mutations (changes).
    