A Pancreatic neuroendocrine tumor, also called an islet cell tumor, is a type of neuroendocrine tumor (NET) that typically arises in the pancreas. However in some cases, a pancreatic NET occurs outside of the pancreas. A NET arises from cells that produce hormones, so the tumor can also produce hormones. It may be benign (not cancerous) or malignant (cancerous). Pancreatic NETs are called either functional or nonfunctional. A functional pancreatic NET causes specific symptoms because it makes extra hormones, such as gastrin, insulin, or glucagon. Examples of types of functional pancreatic NETs include insulinomas, glucagonomas, gastrinomas, VIPomas, and somatostatinomas. Symptoms depend on the type of hormone being made. A nonfunctional pancreatic NET generally does not cause specific symptoms, but may eventually cause symptoms relating to its location and size as it grows or spreads. Most pancreatic NETs are not inherited and occur sporadically in people with no family history of NETs. However, about 10% are associated with a hereditary cancer or tumor syndrome such as multiple endocrine neoplasia type 1 (MEN1), which has autosomal dominant inheritance.