Neurofibroma

What is a neurofibroma?

A neurofibroma is a tumor that forms along peripheral nerves (nerves throughout the body that carry messages to and from the brain and spinal cord). These tumors arise from Schwann cells, a type of cell that helps form the protective sheaths around nerve cells. Neurofibromas can develop on or just under the skin's surface or deeper in the body.

Most neurofibromas develop for no known cause. But in some people, they are linked to neurofibromatosis type 1 (NF1) – a genetic condition that affects development of the nervous system, muscles, bones and skin – and while neurofibromas are usually benign (noncancerous), those that develop with NF1 can become malignant (cancerous).

Typically, neurofibromas are mild in appearance and don't cause pain. But if the tumor is pressing against nerves or growing within them, it can cause uncomfortable symptoms and complications, and may require treatment.

Causes of neurofibroma

Most neurofibromas arise with no clear cause. When they are linked to neurofibromatosis type 1 (NF1), children may develop multiple neurofibromas on their skin and inside their bodies. About 10% of neurofibromas are associated with NF1.

Types of neurofibroma

Neurofibromas can show up in different forms, each with its unique characteristics and potential effects. Main types of neurofibroma include:

• Localized neurofibromas. This is the most common type. They can show up anywhere on the body as small, skin-colored bumps. They don't usually cause any symptoms, though some people are bothered by their appearance. They may grow and become more obvious in adulthood.
• Diffuse neurofibromas. These appear as areas of hardened or thickened skin, typically on the head or neck. They may extend into tissue and fat under the skin. Depending on their size, they may cause some mild numbness.
• Plexiform neurofibromas. This type can appear on the head, neck, torso or limbs and is most common in children with NF1, usually developing before the age of 5. These growths can be large, with multiple nodules (lumps) that have a twisty or winding appearance. Depending on their size and location, plexiform neurofibromas may cause pain or affect body functions. In a small percentage of cases, they become cancerous.
• Atypical neurofibromas. This uncommon type occurs in deeper tissues and is distinguished by how the cells look under a microscope.

Rarely, a neurofibroma becomes a cancerous type of tumor called a malignant peripheral nerve sheath tumor (MPNST). Plexiform and atypical neurofibromas are the types most likely to transform into MPNSTs.

Symptoms of neurofibroma

Neurofibroma symptoms vary widely depending on the tumor's type, size and location. Many neurofibromas cause no symptoms or only mild ones. But tumors that press on nerve fibers may cause pain, tingling, numbness and other neurological problems. Some tumors create lumps or bulges on the skin's surface, affecting physical appearance.

Diagnosis of neurofibroma

Most neurofibromas can be diagnosed during a physical exam. To determine whether they are linked to neurofibromatosis 1, your child's doctor might check for other symptoms or suggest certain tests, including genetic testing.

Neurofibromas deeper in the body are harder to diagnose. They can grow for a long time without causing symptoms and can look like other types of tumors. To diagnose these, doctors might use an MRI, CT scan or electromyogram, which measures electrical activity in muscles. If the doctor suspects your child has plexiform neurofibromas, they may recommend a biopsy or a PET scan to determine whether the tumors are cancerous.

Treatment of neurofibroma

Treatment for neurofibromas depends on the tumor's type, size and location as well as the patient's symptoms. If your child has a localized neurofibroma (one limited to a specific area) that isn't causing bothersome symptoms, the doctor may recommend monitoring – checking regularly for any growth or changes. It’s especially important to keep an eye on plexiform neurofibromas, as they can transform into cancer.

Children with NF1-related neurofibromas benefit by receiving care from a variety of specialists. Our Pediatric Neurofibromatosis Type 1 (NF1) Clinic provides comprehensive care from experts who work as a team.

Surgery for neurofibroma

If a visible neurofibroma is distressing to your child, it can be surgically removed for cosmetic reasons. When neurofibromas are causing pain or neurological issues – diffuse or plexiform types most often do this – removing them surgically can ease symptoms.

In some cases, removal has challenges, which the surgeon will discuss with you. For instance, if a significant amount of skin must be removed, cosmetic surgical techniques may be needed to preserve your child's appearance. Complete removal of plexiform neurofibromas can be complicated due to their intricate growth along nerves; it's often difficult to separate these tumors from the active part of the nerve.

Other options for treating neurofibromas may be available through one of our neurofibromatosis clinical trials, studies that evaluate promising experimental therapies. Learn about the process and potential benefits of participating in a clinical trial at UCSF.