What Is Neuroblastoma?

Cancer starts when cells in the body begin to grow out of control. Cells in nearly any part of the body can become cancer, and can spread to other areas of the body. To learn more about how cancers start and spread, see What Is Cancer?

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

To understand neuroblastoma, it helps to know about the sympathetic nervous system, which is where these tumors start.

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 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 hormones (such as adrenaline [epinephrine]) that help control heart rate, blood pressure, blood sugar, and how the body reacts to stress.

The main cells that make up the nervous system are called nerve cells or neurons. These cells interact 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, Signs and Symptoms of Neuroblastoma).

Neuroblastomas

Neuroblastomas are cancers that start in early nerve cells (called neuroblasts) 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 4 begin in sympathetic nerve ganglia in the abdomen. Most of the rest start in sympathetic ganglia near the spine in the chest or neck, or in the pelvis.

Rarely, a neuroblastoma has spread so widely by the time it is found that doctors can’t tell exactly where it started.

There is a wide range in how neuroblastomas behave. Some grow and spread quickly, while others grow slowly. Sometimes, in very young children, the cancer cells die for no reason and the tumor goes away on its own. In other cases, the cells sometimes mature on their own into normal ganglion cells and stop dividing. This makes the tumor a ganglioneuroma (see below).

Other autonomic nervous system tumors in children

Not all childhood autonomic nervous system tumors are malignant (cancerous).

Ganglioneuroma is a benign (non-cancerous) tumor made up of mature ganglion and nerve sheath cells.

Ganglioneuroblastoma is a tumor that has both malignant and benign parts. It contains neuroblasts (immature nerve cells) that can grow and spread abnormally, similar to neuroblastoma, 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 sure they don’t have areas of malignant cells (which would make the tumor a ganglioneuroblastoma). If the final diagnosis is ganglioneuroma, no other treatment is needed. If it’s found to be a ganglioneuroblastoma, it’s treated the same as a neuroblastoma.