Neuroblastoma is a form of cancer that starts in certain types of very primitive developing nerve cells found in an embryo or fetus. (The term neuro indicates "nerves," while blastoma refers to a cancer that affects immature or developing cells). This type of cancer occurs in infants and young children. It is rarely found in children older than 10 years.

In order to understand neuroblastoma, it helps to know something about the normal structure and function of the sympathetic nervous system.

About the sympathetic nervous system

The nervous system consists of the brain, spinal cord, and the nerves that reach out from them to all areas of the body. The nervous system is essential for thinking, sensation, and movement, among other things.

Part of the nervous system also controls body functions we are rarely aware of, such as heart rate, breathing, blood pressure, digestion, and other functions. This part of the nervous system is known as the autonomic nervous system.

The sympathetic nervous system is a part of the autonomic nervous system. It includes:

• nerve fibers that run along either side the spinal cord

• clusters of nerve cells called ganglia (plural of ganglion) at certain points along the path of the nerve fibers

• nerve-like cells found in the medulla (center) of the adrenal glands. The adrenals are small glands that sit on top of each kidney. These glands make the hormone adrenaline.

The main cells that make up the nervous system are called neurons. These cells communicate with other types of cells in the body by releasing tiny amounts of chemicals (hormones). This is important, because neuroblastoma cells often release certain hormones that can cause symptoms (see the section, "How is neuroblastoma diagnosed?").

How neuroblastomas grow

Neuroblastomas are cancers that start in early nerve cells of the sympathetic nervous system, so they can be found anywhere along this system.

A little more than 1 out of 3 neuroblastomas start in the adrenal glands. About 1 out of 3 begins in the sympathetic nerve ganglia of the abdomen. The rest start in sympathetic ganglia of the chest or neck or in the pelvis.

In rare cases, a neuroblastoma may have spread so widely by the time it is found that doctors can't tell exactly where it started.

Neuroblastomas can behave strangely. Sometimes the cells die without any cause and the tumor disappears. Tumor disappearance is much more common in very young infants than in older children. Another behavior that is unusual for childhood tumors is that the cells sometimes mature spontaneously into normal ganglion cells and stop dividing. This causes the tumor to become a ganglioneuroma (see below).

Other autonomic nervous system tumors

Not all childhood autonomic nervous system tumors are malignant (cancerous). There is a benign tumor called ganglioneuroma which is made up of of mature ganglion and nerve sheaths that do not continue to grow.

Ganglioneuroblastoma is a tumor that has both malignant and benign parts. It contains neuroblasts (immature nerve cells) that can grow and spread abnormally, as well as areas of more mature tissue that are similar to ganglioneuroma.

Ganglioneuromas are usually removed by surgery and looked at carefully under a microscope to be certain they do not have areas of ganglioneuroblastoma. If the final diagnosis is ganglioneuroma, no other treatment is needed. In contrast, ganglioneuroblastomas are treated the same as neuroblastomas (see the section "How is neuroblastoma treated?").

Last Medical Review: 10/22/2008
Last Revised: 10/22/2008