Oncologist-approved cancer information from the American Society of Clinical Oncology
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Neuroendocrine Tumor

This section has been reviewed and approved by the Cancer.Net Editorial Board, 5/2013

ON THIS PAGE: You will find some basic information about this disease and the parts of the body it may affect. This is the first page of Cancer.Net’s Guide to Neuroendocrine Tumor. To see other pages, use the colored boxes on the right side of your screen. Think of those boxes as a roadmap to this full guide. Or, click “Next” at the bottom of each page.

About the endocrine system and endocrine tumors

The endocrine system consists of cells that make hormones. Hormones are chemical substances that are produced by the body and carried through the bloodstream to have a specific effect on the activity of other organs or cells in the body.

A tumor begins when normal cells change and grow uncontrollably, forming a mass. A tumor can be benign or malignant. A benign tumor is not cancerous and usually can be removed without it causing much harm. A malignant tumor is cancerous; if it is not found early and treated, it may be harmful and may spread to and damage the body’s healthy tissues and organs.

An endocrine tumor is a growth that affects the parts of the body that secrete (produce and release) hormones. Because an endocrine tumor arises from cells that produce hormones, the tumor itself can produce hormones and cause serious illness.

About neuroendocrine tumors

A neuroendocrine tumor begins in the hormone-producing cells of the body’s neuroendocrine system, which is made up of cells that are a cross between traditional endocrine cells (or hormone-producing cells) and nerve cells. Neuroendocrine cells are found throughout the body in organs such as the lungs and gastrointestinal tract (including the stomach and intestines). They perform specific functions, such as regulating the air and blood flow through the lungs and controlling the speed at which food is moved through the gastrointestinal tract.

Types of neuroendocrine tumors

There are many types of neuroendocrine tumors. This section focuses on three specific types: pheochromocytoma, Merkel cell cancer, and neuroendocrine carcinoma. Other types of cancer that begin in hormone-producing cells are described in their own sections on Cancer.Net, including endocrine tumors, carcinoid tumorsthymoma, thyroid cancer, and islet cell tumors.

Pheochromocytoma. Pheochromocytoma is a rare tumor that begins in the chromaffin cells of the adrenal gland (specialized cells that release the hormone adrenaline during times of stress). Pheochromocytoma most often occurs in the adrenal medulla, the area inside the adrenal glands. Each person has two adrenal glands, one located on top of each kidney. This type of tumor increases the production of the hormones adrenaline and noradrenaline, which increase blood pressure and heart rate. Even though a pheochromocytoma is usually benign, it may still be life threatening because the tumor may release large amounts of adrenaline into the bloodstream after injury. Eighty percent (80%) of people with pheochromocytoma have a tumor on only one adrenal gland, 10% have tumors on both glands, and 10% have a tumor outside the adrenal glands.

Merkel cell cancer. Merkel cell cancer, also called neuroendocrine carcinoma of the skin or trabular cancer, is a highly aggressive (fast growing), rare cancer. It starts in hormone-producing cells just beneath the skin and in the hair follicles, and it is found in the head and neck region.

Neuroendocrine carcinoma. Approximately 60% of neuroendocrine tumors cannot be described as a specific type of cancer other than neuroendocrine carcinoma. Neuroendocrine carcinoma can start in a number of places in the body, including the lungs, brain, and gastrointestinal tract.

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