Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Pancreatic Neuroendocrine Tumors (Islet Cell Tumors) ?
    ### Response:
    Key Points
                    - Pancreatic neuroendocrine tumors form in hormone-making cells (islet cells) of the pancreas.    - Pancreatic NETs may or may not cause signs or symptoms.    - There are different kinds of functional pancreatic NETs.     - Having certain syndromes can increase the risk of pancreatic NETs.
    