Neuroendocrine tumors remain relatively uncommon. However, the most recent studies show that by 2012, the incidence in the United States had risen to approximately 7 in 100,000, which means more than 20,000 new cases a year. Survival rates have also increased over time. A retrospective review of the SEER data (Dasari, et al.) estimated the prevalence of neuroendocrine tumors in the United States at over 170,000 in 2014.

The incidence of the tumors by primary site (2012 data) is approximately:
23% lung
18% small intestine
16% rectum
12% pancreas
7% stomach
10% other gastroenteropancreatic or GEP-NETs(appendix, colon, cecum)
14% unknown primary site

Rare sites include the uterus, ovary, testis, breast, adrenal glands and larynx.