Benign Peripheral Nerve Tumors: Symptoms, Causes, and Treatment
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 17, 2026
Quick Answer
A benign peripheral nerve tumor is a non-cancerous growth on a peripheral nerve, one of the nerves linking the brain and spinal cord to muscles and tissues. Schwannoma is the most common type in adults. Symptoms include a lump, pain, tingling, numbness or weakness. Treatment is watchful waiting or surgery, usually only for large or symptomatic tumors or cancer concerns.
What the research says
MRI is good at separating benign from malignant nerve sheath tumors. A meta-analysis of 15 studies (798 lesions: 252 malignant and 546 benign) found pooled sensitivity of 68% and specificity of 93% using combined MRI features. Using diffusion restriction, sensitivity rose to 88% and specificity to 94% (Wilson et al., AJR Am J Roentgenol, 2021) [3].
In NF1, the lifetime risk of a cancerous nerve sheath tumor is real but limited. The overall lifetime risk of malignant peripheral nerve sheath tumor (MPNST) in neurofibromatosis type 1 is estimated at 8% to 13%, higher with certain germline mutations and a larger benign tumor burden (Gross et al., Neurooncol Adv, 2026) [4].
Rarely, a cancer can look like a benign schwannoma. A review of 39 MPNST cases in schwannomatosis found these tumors can arise even without prior radiation and may mimic benign schwannomas, which is why vigilant follow-up matters (Porche et al., J Neurosurg, 2026) [5].
Study details are from PubMed abstracts.
What are benign peripheral nerve tumors?
Benign peripheral nerve tumors are tumors that form on peripheral nerves. The peripheral nerves link the brain and spinal cord to other parts of the body. These nerves control muscles that allow you to walk, blink, swallow, pick things up, and do other activities. Benign tumors are not cancerous. [1]
Peripheral nerve tumors affect nerves by growing within them or by pressing against them. Tumors that grow within nerves are called intraneural tumors. Tumors that press against nerves are called extraneural tumors. [1]
Although most of these tumors are not cancerous, they can cause nerve damage and loss of muscle control. That is why it is important to see a healthcare professional if you have a lump, or if you have pain, tingling, numbness, or muscle weakness. [1]
What are the five types of benign peripheral nerve tumors?
Several different types of tumors may form on the peripheral nerves. While some are caused by genetics, the cause of these tumors is usually not known. [1]
Schwannoma
A schwannoma is the most common benign peripheral nerve tumor in adults. These nerve sheath tumors are called schwannomas because they are made up of Schwann cells, which surround the nerves. They usually grow slowly. If you develop a schwannoma in an arm or leg, you might notice a mass, but you might have one for years before noticing it. [1]
A schwannoma typically comes from a single bundle of nerve fibers, called a fascicle, within the main nerve. When a schwannoma grows, more fascicles are at risk when trying to remove the tumor safely. Schwannomas most commonly occur alone; occasionally, some people have several of them in the arms, legs, or body, a condition called schwannomatosis. [1]
A rare schwannoma near the brainstem, known as an acoustic neuroma (or vestibular schwannoma), can cause trouble with balance or hearing. If acoustic neuromas are not treated and they continue to grow, they can affect nearby nerves and press on the brainstem. [1]
Neurofibroma
This common type of benign nerve tumor tends to form in the center of a nerve and may arise from several nerve bundles. It tends to cause mild symptoms. It most commonly develops in people with a genetic condition that causes tumors to grow on nerves, known as neurofibromatosis type 1 (NF1). [1]
Perineurioma
This rare benign peripheral nerve tumor arises from perineurial cells, which surround the peripheral nerve sheath. It can form within a nerve (intraneural perineurioma) or in soft tissue next to a nerve (extraneural perineurioma). An intraneural perineurioma happens most often in children and young adults, and typically causes gradually progressive weakness in an arm or leg. [1]
Lipoma
Slow-growing fat cells cause this benign, soft lump that usually appears under the skin on the neck, shoulders, back, or arms. A lipoma near a nerve can squeeze it. Usually, though, a lipoma causes no pain or other problems, and a healthcare professional might monitor it through regular checkups. [1]
Ganglion cyst
Some ganglion cysts come from an injury, but most have no known cause. They commonly form near joints, such as the wrist, and can cause pain and interfere with everyday activities. Some go away without treatment, but ganglion cysts that press on or are in nerves need to be treated. [1]
A more complex nerve sheath tumor may also assume the shape of a dumbbell. This type of tumor occurs in the spine and lower abdomen and is intertwined with important nerves. [1]
What are the symptoms of benign peripheral nerve tumors?
Symptoms depend on the location of the benign peripheral nerve tumor and the nerves and tissues it affects. A tumor can cause symptoms if it presses on the nerve in which it is growing, and it can also press on nearby nerves, blood vessels, or tissues. As a tumor grows, it may be more likely to cause symptoms, but even small tumors can cause symptoms. [1]
Symptom | What you may notice |
Swelling or a lump | A lump under the skin, sometimes visible or easy to feel |
Pain, tingling, or numbness | Pinching, pins-and-needles, or reduced feeling in the area the nerve serves |
Weakness or loss of function | Trouble using the muscles in the affected area |
Dizziness or loss of balance | Mostly with tumors near the brainstem, such as an acoustic neuroma |
It is important to see a healthcare professional if you have a lump, or if you have pain, tingling, numbness, or muscle weakness. [1]
What causes benign peripheral nerve tumors?
The cause of benign peripheral nerve tumors usually is not known. Some are passed down in families. [1]
Risk factor | What it means |
Neurofibromatosis type 1 (NF1) | A genetic condition that raises the risk of neurofibromas; NF1 can cause several of them. NF1 also raises the risk of a malignant (cancerous) peripheral nerve sheath tumor, so regular check-ins with a healthcare professional matter. Most people who have neurofibromas do not have NF1 |
Schwannomatosis gene | Having the gene that causes schwannomatosis is a risk factor for schwannomas |
Family history | Some of these tumors are passed down in families, though most cases have no known cause |
How are benign peripheral nerve tumors diagnosed?
To diagnose a peripheral nerve tumor, a healthcare professional runs tests to find where the tumor is located and what type of tumor it is. [2]
Test | What it does |
MRI | The preferred method for imaging peripheral nerve tumors; uses a magnetic field and radio waves to produce a detailed 3D view of the nerves and surrounding tissue, and shows whether a tumor is inside or outside the nerve |
CT scan | Rotates around the body to record a series of images; not as useful as MRI for these tumors, but used if you cannot have an MRI or if more detail about nearby bone is needed |
Electromyogram (EMG) | Records the electrical activity in a muscle when you try to move it; helps locate the tumor and identify which nerves are involved |
Nerve conduction study | Usually done along with the EMG; measures how quickly nerves carry electrical signals to the muscles |
Tumor biopsy | A small sample of cells is removed and studied; local or general anesthesia may be used depending on size and location; done with a needle guided by imaging, or during surgery |
Nerve biopsy | A small tissue sample is sent to a lab to look for signs of cancer and help diagnose the tumor type |
How are benign peripheral nerve tumors treated?
Treatment of peripheral nerve tumors involves either surgical removal or watching the tumor for changes. If there is a low chance that the tumor may become cancerous and it is not causing symptoms, you might not need surgery. [2]
Your healthcare professional might also recommend observation if your tumor is in a place that makes it hard to remove. Observation includes regular checkups and imaging tests to see if the tumor is growing. [2]
Surgery may be needed if there is a concern that the tumor is cancerous. The tumor may also be surgically removed if it is large or causing pain or other symptoms, such as weakness, numbness, or tingling. [2]
During schwannoma surgery, surgeons carefully remove the tumor while taking care to preserve bundles of nerve fibers, called fascicles, that are not affected by the tumor. [1]
Path | When it is used | What happens |
Watchful waiting (observation) | Low chance of becoming cancerous and no symptoms, or a tumor in a hard-to-reach spot | Regular checkups and imaging tests to see if the tumor is growing |
Surgery | Concern the tumor may be cancerous, the tumor is large, or it causes pain, weakness, numbness, or tingling | The tumor is removed, ideally while protecting unaffected nerve fiber bundles |
What should you do before your appointment?
You might be referred to a doctor who specializes in nervous system conditions, known as a neurologist, or to a doctor trained in brain and nervous system surgery, known as a neurosurgeon. [2]
Before the visit, write down when you first noticed symptoms and whether they have changed over time. Write down your key medical information, including any surgeries. Make a list of all your medications, vitamins, or supplements, including the doses. Find out if anyone in your family has ever had similar problems. Ask a family member or friend to accompany you to help you remember what you learn during the appointment, and write down questions to ask. [2]
Questions worth asking include: What is the most likely cause of the problem? What kinds of tests do I need? What treatments are available? I have other health conditions, so how can I best manage them together?
Your healthcare professional will likely ask questions of their own, such as whether you have pain and where it is, whether you have any weakness, numbness, or tingling, whether your symptoms have been continuous or occasional, and what treatments you have already tried. [2]
What is the bottom line on benign peripheral nerve tumors?
A benign peripheral nerve tumor is not cancer, but it is still worth taking seriously. These growths form on the nerves that carry signals between the brain, spinal cord, and the rest of the body, and even small ones can press on a nerve and cause pain, tingling, numbness, or weakness. [1]
The five types behave very differently. A schwannoma, the most common in adults, may sit quietly for years. A perineurioma most often shows up in children and young adults as gradually worsening weakness. A lipoma or ganglion cyst near a wrist is usually a minor matter. What matters most is not the label but three questions: What type is it, is it affecting nerve function, and is there any concern it could become cancerous? [1] [2]
The two treatment paths are simple: watch it, or remove it. If the chance of it becoming cancerous is low and it causes no symptoms, watching with regular checkups and imaging is often enough. Surgery comes into play when the tumor is large, causes pain or weakness, or raises concern. [2]
The first and most important step is a proper diagnosis. An MRI, the preferred imaging test, can show whether a lump sits inside a nerve or presses against it, and a small tissue sample can confirm what the growth is. If you have a lump, or pain, tingling, numbness, or muscle weakness, a visit to a healthcare professional is the right next move.
Next steps: If you have noticed a lump, or ongoing pain, tingling, numbness, or weakness, schedule a visit with a healthcare professional. Write down when symptoms started, what seems to make them better or worse, and any family history of nerve tumors.
FAQ
Is a benign peripheral nerve tumor cancer?
No. Benign tumors are not cancerous. However, they can press on nerves and cause pain, numbness, tingling, or muscle weakness, and some people with certain genetic conditions have a higher risk of cancerous nerve sheath tumors, which is why a professional evaluation matters.
What are the most common symptoms?
The main symptoms are swelling or a lump under the skin, pain, tingling, or numbness, weakness or loss of function in the affected area, and, for tumors near the brainstem such as an acoustic neuroma, dizziness or loss of balance.
Do all benign nerve tumors need surgery?
No. If the chance of the tumor becoming cancerous is low and it is not causing symptoms, surgery may not be needed. Observation with regular checkups and imaging is often recommended, especially for tumors in places that are hard to reach.
How is a peripheral nerve tumor diagnosed?
Doctors use an MRI, the preferred imaging test, along with an electromyogram (EMG) and nerve conduction study to locate the tumor and identify the affected nerves. A biopsy may follow to confirm the type and check for cancer.
Can these tumors run in families?
Yes. Some benign nerve tumors are passed down in families. The genetic condition NF1 raises the risk of neurofibromas, and the schwannomatosis gene raises the risk of schwannomas. Most people with these tumors, however, do not have a known genetic cause.
Disclaimer: This article is for general informational purposes only and does not constitute medical advice. Always consult a qualified health care provider for individual questions.
References
Mayo Clinic Staff. Benign peripheral nerve tumor - Symptoms and causes. Mayo Clinic. January 10, 2025. https://www.mayoclinic.org/diseases-conditions/peripheral-nerve-tumors-benign/symptoms-causes/syc-20368680
Mayo Clinic Staff. Benign peripheral nerve tumor - Diagnosis and treatment. Mayo Clinic. January 10, 2025. https://www.mayoclinic.org/diseases-conditions/peripheral-nerve-tumors-benign/diagnosis-treatment/drc-20504138
Wilson MP, et al. Diagnostic Accuracy of MRI for the Detection of Malignant Peripheral Nerve Sheath Tumors: A Systematic Review and Meta-Analysis. AJR Am J Roentgenol. 2021;217(1):31-39. PMID 33909462. https://doi.org/10.2214/AJR.20.23403
Gross AM, et al. Malignant peripheral nerve sheath tumor development during MEK inhibitor treatment: A pre-clinical study and a clinical case series. Neurooncol Adv. 2026;8(1):vdag180. PMID 42540436. https://doi.org/10.1093/noajnl/vdag180
Porche K, et al. Malignant peripheral nerve sheath tumors in schwannomatosis: systematic review and meta-analysis. J Neurosurg. 2026;144(3):642-652. PMID 41237393. https://doi.org/10.3171/2025.6.JNS251508
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