Overview of Neuroendocrine Tumors
Neuroendocrine tumors (NET) are classically divided into 2 categories: carcinoid tumors and pancreatic neuroendocrine tumors (PNET).1 Carcinoid tumors are derived from enterochromaffin cells throughout the gastrointestinal (GI) and bronchopulmonary systems.2,3 The most common sites for primary GI carcinoid tumors are the colon, rectum, and appendix3 (Figure 1). Approximately 9.4% of NET are PNET.4
Figure 1. Distribution of Carcinoid Tumors by Site3,4

NET can also be located in the parathyroid, adrenal gland, pituitary glands, ovary, heart, and ear.1,5
NET were once considered to be rare neoplasms; however, over the past 30 years, there has been a 5-fold increase in their incidence.2,6 The annual age-adjusted incidence of NET is 5.25 per 100,0006; it is 5.35 per 100,000 in men compared with 4.76 per 100,000 in women.7 NET are more common in individuals over 50 years of age7, as well as in white patients (81%).6 The prevalence is 35 cases per 100,000 in the United States population (103,312), making NET the second most common Gl malignancy after colorectal cancer.6,8