Neuroendocrine tumors (NETs) are those that arise from neuroendocrine cells found throughout the body. Neuroendocrine cells act like nerve cells (neurons), but they also produce hormones like cells of the endocrine system (endocrine cells) that control metabolism, digestion, and other bodily functions.
Neuroendocrine tumors are classified by their site of origin, usually either pancreatic neuroendocrine tumors (which start in the pancreas) or carcinoid tumors (which most commonly start in the lungs, small intestine, appendix, or rectum).
The terms carcinoid tumor and carcinoid cancer are old ways of describing slow-growing neuroendocrine tumors.
What Are Symptoms of Carcinoid and Neuroendocrine Tumors?
General symptoms of neuroendocrine tumors may include:
- Fatigue
- Loss of appetite
- Unexplained weight loss
Symptoms related to the tumor size and/or location of neuroendocrine tumors may include:
- Chronic pain in a specific area
- A lump in any part of the body
- Nausea or vomiting
- Persistent cough
- Hoarseness
- Changes in bowel or bladder habits
- Yellowing of the skin and whites of the eyes (jaundice)
- Unusual bleeding or discharge
Symptoms of neuroendocrine tumors related to the release of hormones may include:
- Diarrhea
- Facial flushing, usually without sweating
- High blood sugar (hyperglycemia)
- Frequent urination
- Increased thirst
- Increased hunger
- Low blood sugar (hypoglycemia)
- Ulcers
- Skin rash
- Confusion
- Anxiety
- Nutritional deficiencies, such as niacin and protein deficiency
What Causes Carcinoid and Neuroendocrine Tumors?
The cause of most carcinoid and neuroendocrine tumors is unknown.
Risk factors for developing a NET include:
- Inherited syndromes
- Race/ethnicity
- More common in white people than Black people
- Gender
- Slightly more common in women than in men
- Age
- Rare in children, though people of any age can develop a NET
- Other medical conditions
- Diseases that damage the stomach and reduce acid production
How Are Carcinoid and Neuroendocrine Tumors Diagnosed?
Most carcinoid and neuroendocrine tumors are found when people have tests or medical procedures done for other reasons not related to the tumor. If a NET is suspected, diagnostic tests may include:
- Biopsy
- Blood tests
- Urine tests
- 5-HIAA
- Molecular testing of the tumor to identify specific genes, proteins, and other factors unique to the tumor which may help determine treatment options
- Endoscopy
- Imaging tests
- Ultrasound
- X-ray
- Computed tomography (CT or CAT) scan
- Magnetic resonance imaging (MRI)
- Nuclear medicine imaging
What Is the Treatment for Carcinoid and Neuroendocrine Tumors?
Treatment for carcinoid and neuroendocrine tumors depends on the symptoms, where the tumor originated, how fast the tumor is growing, and how much the cancer has spread.
Treatment may include one or more of the following:
- Active surveillance (also called watchful waiting)
- Used for low-grade NETs that grow slowly and not spread or cause symptoms for a long time
- The tumor is monitored with regular testing
- Treatment starts if the tumor shows signs of growing or spreading
- Surgery
- Removal of the tumor with some surrounding tissue (margins)
- Most localized NETs can be successfully treated with surgery alone
- If complete removal of the tumor is not possible, debulking surgery may be performed to remove as much of the tumor as possible and provide some relief from symptoms, though it is not a cure
- Medications
- Somatostatin analogs
- Octreotide (Sandostatin)
- Lanreotide (Somatuline Depot)
- Chemotherapy
- Targeted therapy
- Everolimus (Afinitor)
- Sunitinib (Sutent)
- Immunotherapy
- Interferon alfa-2b (Intron A)
- Peptide receptor radionuclide therapy (PRRT)
- Lu-dotatate (Lutathera)
- Somatostatin analogs
- Radiation therapy
- External beam radiation
- Liver-directed treatment if the cancer has spread to the liver
From 
https://www.cancer.net/cancer-types/neuroendocrine-tumors/introduction