Neuroendocrine cells are present in various parts of the body and have the characteristics of nerve and hormone-producing cells. These cells are commonly found in the gastrointestinal tract, lungs, appendix, and pancreas. When these cells undergo uncontrolled cell division, they form a neuroendocrine tumor (NET). Some of the tumors grow quickly, while others have slow growth. Some NETs release excessive hormones that cause symptoms in most patients.
