Neurofibroma

Overview

A neurofibroma is a type of peripheral nerve tumor that forms a soft bump on or under the skin. The tumor can develop within a major or minor nerve anywhere in the body.

This common type of nerve tumor tends to form centrally within the nerve. A neurofibroma forms on the protective covering of the nerve, known as the nerve sheath. Sometimes it grows on several nerve bundles. When this happens, it's called a plexiform neurofibroma.

A neurofibroma may cause mild symptoms or no symptoms at all. If the tumor presses against nerves or grows within them, it may cause pain or numbness.

A neurofibroma usually isn't cancer. Rarely, it can become cancer.

Symptoms

A neurofibroma might cause no symptoms. If symptoms occur, they're usually mild. When a neurofibroma grows on or under the skin, symptoms may include:

• A bump on the skin. The bump may be the color of your skin or pink or tan.
• Pain.
• Bleeding.

If a neurofibroma becomes large or presses against or grows on a nerve, symptoms may include:

• Pain.
• Tingling.
• Numbness or weakness.
• Change in appearance when a large neurofibroma is on the face.

Some people with neurofibromas have a genetic condition known as neurofibromatosis type 1 (NF1). A person with NF1 may have many neurofibromas. The number of neurofibromas increases with age.

A tumor that involves many nerves, known as a plexiform neurofibroma, can occur in a person with NF1. This type of neurofibroma can grow large and cause pain. It also can become cancerous.

Causes

A neurofibroma can arise with no known cause, or it may appear in people with a genetic condition called neurofibromatosis type 1. Neurofibromas most often are found in people ages 20 to 30 years old.

Risk factors

The only known risk factor for neurofibromas is having the genetic condition known as neurofibromatosis type 1 (NF1). People with NF1 have several neurofibromas, along with other symptoms. In about half of the people with NF1, the disease was passed down from a parent. However, most people with neurofibromas don't have NF1.