Islet cell tumors are cancerous tumors that form in the pancreas, but they are a rare form of pancreatic cancer. Normal islet cells produce insulin and hormones that aid in digestion. Causes of different types of islet cell tumors may include genetics and those with certain conditions such as tuberous sclerosis or von Hippel-Lindau disease. Symptoms may include abdominal pain, dizziness, diarrhea, headache, nausea, and more. Doctors may treat these tumors with surgery, radiation, medications, or other methods. Follow the links below to find WebMD's comprehensive coverage about how islet cell tumors form, how to treat them, and much more.