Words to know: Neuroendocrine tumors (NETs)
- Neuroendocrine cell
- A cell that acts partly like a nerve cell and partly like a hormone-making cell. NETs start in these cells.
- Neuroendocrine tumor (NET)
- A tumor that starts in neuroendocrine cells. Most grow slowly.
- Carcinoid tumor
- An older name for a NET, still used for some NETs of the lung and intestine.
- Neuroendocrine carcinoma (NEC)
- A fast-growing, poorly differentiated neuroendocrine cancer that is treated differently from NETs.
- Well-differentiated
- Tumor cells that still look fairly like normal cells. These tend to grow more slowly.
- Grade
- A measure of how fast tumor cells are growing, based on Ki-67 and cell counts under a microscope.
- Ki-67
- A lab marker that shows what share of tumor cells are dividing. Higher numbers mean faster growth.
- Functional tumor
- A tumor that makes enough hormones to cause symptoms.
- Carcinoid syndrome
- Symptoms such as flushing, diarrhea, and wheezing caused by chemicals like serotonin made by some NETs, usually after spread to the liver.
- Carcinoid crisis
- A rare, sudden, serious flare of carcinoid symptoms with low blood pressure. It can happen during surgery or procedures.
- Carcinoid heart disease
- Thickening and damage of heart valves caused by long-term high serotonin.
- Serotonin
- A body chemical made in large amounts by some NETs. It causes many carcinoid syndrome symptoms.
- 5-HIAA
- A breakdown product of serotonin, measured in urine or blood to check for carcinoid syndrome.
- Chromogranin A
- A protein released by many NETs that can be measured in the blood.
- Somatostatin
- A natural hormone that turns down the release of other hormones.
- Somatostatin receptor
- A docking spot for somatostatin found on most NET cells. Scans and treatments can target it.
- Somatostatin analog
- A man-made drug that acts like somatostatin, such as octreotide or lanreotide. It calms symptoms and slows tumor growth.
- Somatostatin receptor PET scan
- A scan using a radioactive tracer that sticks to somatostatin receptors, such as Ga-68 DOTATATE or Cu-64 DOTATATE.
- PRRT
- Peptide receptor radionuclide therapy. A radioactive medicine, such as Lu-177 dotatate, that travels to NET cells and treats them with radiation.
- Everolimus
- A daily pill that blocks the mTOR growth signal in tumor cells.
- Insulinoma
- A pancreatic NET that makes too much insulin and causes low blood sugar.
- Gastrinoma
- A NET that makes too much gastrin, causing stomach ulcers and diarrhea.
- MEN1
- Multiple endocrine neoplasia type 1, an inherited condition that raises the risk of NETs and other gland tumors.
- Embolization
- A treatment that blocks the blood supply to tumors in the liver.
- Clinical trial
- A research study that tests new treatments in people.
Last updated: 2026-10-27. Medically reviewed by Veli Bakalov, MD, medical oncologist (October 2026). General education from Step by Step, the patient portal of HemeOncBuddy.