Plexiform Neurofibroma

Overview

A plexiform neurofibroma is a benign (non-cancerous) tumor that develops from the cells surrounding nerves. Unlike a simple skin neurofibroma, it grows along the length of a nerve and can extend into many of its branches, sometimes spreading through nearby tissue in a tangled, rope-like network. This is why it is described as "plexiform," meaning braided or interwoven.

These tumors are most commonly seen in people with neurofibromatosis type 1 (NF1), a genetic condition. They are usually present from an early age and tend to grow slowly over time. Although the tumor itself is not cancer, a plexiform neurofibroma can cause problems by pressing on or distorting nearby structures, and in a minority of cases it can change over time, so it is monitored.

Symptoms

Symptoms depend on where the tumor is and how large it grows. Small ones may cause nothing noticeable, while larger or deeper ones can produce:

• A soft, sometimes lumpy swelling under the skin that can feel like a "bag of worms"
• Darkened or thickened overlying skin, sometimes with excess hair
• Disfigurement or asymmetry if the tumor is large
• Pain, tingling, numbness, or weakness if a nerve is affected
• Pressure-related problems, such as breathing or vision changes, depending on location

A plexiform neurofibroma that suddenly grows faster, becomes firm, or develops new constant pain should be evaluated promptly, because these can be warning signs of a change in the tumor.

Causes

Plexiform neurofibromas arise from changes in the cells of the nerve sheath, the protective covering around nerves. In most cases they are linked to neurofibromatosis type 1.

• Neurofibromatosis type 1 (NF1): A genetic condition caused by changes in the NF1 gene. This gene normally helps keep cell growth in check, and when it does not work properly, nerve-sheath tumors such as plexiform neurofibromas can form.
• Inherited or new gene changes: NF1 can be passed down in a family or can arise as a new gene change in a person with no family history.

Because these tumors are so closely tied to NF1, finding a plexiform neurofibroma often prompts evaluation for the broader condition.

Risk Factors

• Having neurofibromatosis type 1, by far the most important factor
• A family history of NF1
• Other NF1 features such as multiple cafe-au-lait spots, freckling, and skin neurofibromas
• Childhood, since plexiform tumors are often present early and grow during years of body growth

Diagnosis

Diagnosis combines examination with imaging:

• Physical examination: Feeling the lump and checking for nerve symptoms and other signs of NF1.
• MRI scanning: The main imaging test, showing the size, extent, and relationship of the tumor to nerves and nearby structures.
• Other imaging: Specialized scans may be used to look for areas of concern within a large tumor.
• Biopsy: Sometimes done if there is worry about a change in the tumor, to examine the tissue under a microscope.

Treatment

Treatment is tailored to the individual and depends on the tumor's size, location, symptoms, and rate of growth. Many small, stable tumors simply need monitoring.

• Observation: Regular check-ups and scans for tumors that are not causing problems.
• Medication: For some patients, particularly children with NF1 and a tumor that cannot be removed safely, targeted drug therapy can be used to shrink the tumor or slow its growth, under specialist care.
• Surgery: May be considered to relieve pressure, pain, or disfigurement, though complete removal can be difficult because the tumor weaves through tissue and nerves.
• Multidisciplinary care: Specialists in NF1 coordinate treatment because of the tumor's complexity.

Any sudden change in a known plexiform neurofibroma should be assessed quickly so that appropriate testing can be done.

Prevention

Plexiform neurofibromas cannot be prevented, because they result from genetic changes. The practical focus is on early detection and monitoring:

• People with NF1 benefit from regular specialist follow-up to track known tumors
• Report any new, growing, or painful lump promptly
• Genetic counseling can help families understand inheritance and options

When to See a Doctor

See a doctor if you or your child has:

• A new soft lump under the skin, especially with other signs of NF1
• A known plexiform neurofibroma that suddenly grows faster or becomes firm
• New constant or worsening pain in the area of the tumor
• Numbness, weakness, or loss of function in the affected part of the body

Persistent new pain or rapid growth deserves prompt evaluation, as these features can signal a change in the tumor that needs specialist assessment.

Related Topics

Frequently Asked Questions

References

1. National Institute of Neurological Disorders and Stroke (NINDS). Neurofibromatosis.
2. National Cancer Institute (NCI). Neurofibromatosis type 1.
3. MedlinePlus, U.S. National Library of Medicine. Neurofibromatosis 1.
4. Children's Tumor Foundation. Plexiform Neurofibromas.