Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Salivary Gland Cancer ?
    ### Response:
    Key Points
                    - Salivary gland cancer is a rare disease in which malignant (cancer) cells form in the tissues of the salivary glands.    - Being exposed to certain types of radiation may increase the risk of salivary cancer.     - Signs of salivary gland cancer include a lump or trouble swallowing.
    