Neuroendocrine tumors are abnormal growths that begin in the hormone-producing cells of the body’s neuroendocrine system, which is made up of cells similar to nerve cells and are located throughout the body. They perform specific functions such as regulating the air and blood flow through the lungs and controlling the speed at which food is moved through the gastrointestinal tract. Neuroendocrine tumors most commonly occur in the lungs, small intestine, and appendix. Symptoms and treatment of this condition are dependent on the location of the tumor. These tumors can occur all over the body so identifying the symptoms and proper treatment is often difficult.