Factors that increase risk

• Age. Some neuroendocrine tumors such as a rare adrenal gland tumor called pheochromocytoma is most common between the ages of 40 and 60, while Merkel cell cancer, another type of neuroendocrine tumor, is most common in people over the age of 70. 
• Immune system suppression. People with human immunodeficiency virus (HIV) and people whose immune systems are suppressed because of an organ transplant have a higher risk of developing a neuroendocrine tumor.

Inherited neuroendocrine cancer clues

Most pancreatic neuroendocrine tumors are not inherited, but they can be seen in inherited familial syndromes such as multiple endocrine neoplasia type 1 and 2, von Hippel-Lindau disease, neurofibromatosis type 1, tuberous sclerosis and Carney complex.