Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Prostate Cancer ?
    ### Response:
    Key Points
                    - Prostate cancer is a disease in which malignant (cancer) cells form in the tissues of the prostate.    - Signs of prostate cancer include a weak flow of urine or frequent urination.     - Tests that examine the prostate and blood are used to detect (find) and diagnose prostate cancer.
    