Nerve Sheath Tumours: Schwannomas and Neurofibromas
Expert guidance from Mr Ashley Simpson, Consultant Peripheral Nerve Surgeon. Symptoms, MRI, surgery, recovery and UK referral routes — for patients and referrers alike.
What Are Nerve Sheath Tumours?
The Basics
Nerve sheath tumours are growths arising from the tissue around a nerve. The two best-known benign types in peripheral nerve practice are schwannoma and neurofibroma. They are uncommon but important — they can cause pain, pins and needles, numbness, weakness, or a lump mistaken for a cyst or lipoma.
Most lesions are benign. The key questions are: what is it, is it arising from the nerve itself, is it safe to observe, does it need surgery, and are there any red flags for malignancy or an underlying genetic condition?
Schwannoma vs Neurofibroma
A schwannoma develops from Schwann cells and typically sits eccentrically on the parent nerve, displacing functioning fascicles rather than engulfing them.
A neurofibroma is more often central within the nerve, involves multiple fascicles, and can therefore be harder to remove without neurological trade-offs.
Both can present with a lump and nerve symptoms, but the exact relationship to the nerve affects surgical planning and risk — which is why specialist assessment matters.
Symptoms, Red Flags and Diagnosis
Common Symptoms
Patients typically describe a slow-growing lump, pain on pressure, tingling or electric-shock sensations, altered sensation, or weakness.
In one 150-case review, pre-operative features included paraesthesia in 77%, pseudo-Tinel symptoms in 55%, pain in 50%, and hypoaesthesia in 18%.
Misdiagnosis Risk
A lump with nerve pain, pins and needles, numbness or weakness should not be assumed to be a simple lipoma or cyst.
A specialist-centre series found an incorrect primary diagnosis in 45% of benign peripheral nerve sheath tumours, with inappropriate surgery in 26% of wrongly diagnosed cases and severe neurological deficits in those patients.
Diagnostic Hierarchy
- Clinical examination — nerve distribution, Tinel-like signs, sensory and motor assessment
- Ultrasound — useful triage, but operator-dependent
- MRI — most informative for planning; shows fusiform shape, split-fat sign, target sign, entering/exiting nerve
- Electrophysiology — helpful where functional deficit or diagnostic uncertainty exists
Seek urgent specialist assessment if: the lump is increasing in size, becomes hard, causes new or worsening pain especially at night, produces new weakness or spreading numbness, or imaging is suspicious or indeterminate for sarcoma. In adults, NICE recommends urgent direct-access ultrasound for an unexplained growing lump, and suspected-cancer referral if ultrasound is suggestive of sarcoma or remains uncertain.
Schwannoma vs Neurofibroma: Key Differences
Understanding the distinction guides surgical planning and risk counselling. The table below synthesises imaging, pathology and peripheral nerve surgery literature.
Causes and Associated Genetic Conditions
Many schwannomas and solitary neurofibromas are sporadic — arising without a known inherited cause. However, multiple tumours, earlier presentation, or specific MRI patterns should prompt consideration of a tumour predisposition syndrome.
The most relevant UK conditions are NF1, NF2-related schwannomatosis, and other forms of schwannomatosis. Plexiform neurofibroma is strongly associated with NF1. Multiple schwannomas may indicate NF2-related schwannomatosis
NF1
Tumours grow on nerves and skin; plexiform neurofibroma is a hallmark feature
NF2-Related Schwannomatosis
Multiple schwannomas; bilateral vestibular schwannomas typical
Schwannomatosis
Multiple schwannomas without NF2 features; often painful
For patients with known or suspected NF1: rapid change, increasing pain, new neurological deficit or loss of previously benign imaging features may indicate malignant peripheral nerve sheath tumour (MPNST). This should trigger sarcoma/NF review — not routine observation.
Surgery: When It Is Needed and How It Is Done
Not every tumour needs immediate surgery. Surgery is usually considered when the lesion is painful, growing, symptomatic, function-threatening, diagnostically uncertain, cosmetically troublesome, or suspicious for malignant change.
1
Schwannoma Technique
Microsurgical intracapsular or interfascicular enucleation through a safe fascicular window, with meticulous dissection in the correct plane and preservation of functioning fascicles
2
Neurofibroma Technique
More variable — nerve-sparing microdissection where possible; limited debulking, subtotal excision, or resection with reconstruction if the functional trade-off is justified
3
Intra-operative Monitoring
Neurophysiological monitoring or direct stimulation is particularly useful for major mixed nerves, deep lesions, brachial plexus lesions, larger tumours, and uncertain nerve-tumour interfaces
Do not undertake casual excision biopsy of a suspected intraneural mass outside a specialist pathway. Benign PNSTs are frequently mislabelled as ordinary soft-tissue masses, and unplanned excision can create avoidable neurological damage.
Expected Outcomes and Surgical Risks
Mr Ashley Simpson has published the largest single-centre case series on peripheral nerve schwannomas to date — 531 cases treated at the Peripheral Nerve Injury Unit, Royal National Orthopaedic Hospital, Stanmore. The results are reassuring: the vast majority of patients do very well after surgery, serious complications are rare, and no cases of malignant transformation or recurrence were recorded.
~70%
Completely asymptomatic after surgery
0.6%
Rate of significant motor deficit
0%
Malignant transformation or recurrence
These results support microsurgical excision at a specialist centre as a safe and effective treatment. Patients should be counselled that temporary sensory changes are possible, but serious permanent weakness is uncommon.
Before and After Surgery
Before Surgery
Confirm the diagnosis pathway, review MRI and previous imaging, document baseline nerve function, and discuss whether observation is reasonable.
Patients should be warned about numbness, temporary or permanent weakness, neuropathic pain, bleeding, infection, scar sensitivity, incomplete excision, and the possibility that final histology changes management. Many procedures are day-case or overnight-stay operations.
After Surgery & Recovery
Most patients go home the same day. The wound usually heals over about 2 weeks, with a dressing/wound review commonly arranged at that time when histology is often available.
Early soreness and bruising are common and occasionally altered sensation; nerve symptoms may continue improving gradually over weeks to months. Simple analgesia taken regularly in the first 24–48 hours is more effective than waiting for pain to flare.
Scar Care
Keep the wound clean and dry until advised otherwise. Once healed, use a plain moisturiser, protect the scar from UV light, and begin gentle scar massage.
Light massage is advised for 5–10 minutes twice daily, increasing pressure after 6 weeks if comfortable. Physiotherapy should be arranged promptly where there is stiffness, weakness, oedema, scar tethering, or return-to-work demands.
Contact your surgical team, GP or NHS 111 urgently if the wound becomes red, hot, swollen, increasingly painful, opens up, leaks pus, or you develop fever or feel unwell. Wound infection can appear from 2–3 days after surgery until the wound is healed (usually 2–3 weeks, occasionally later).
Frequently Asked Questions
Common questions about nerve sheath tumours, answered by Mr Ashley Simpson.
Can a schwannoma or neurofibroma be cancer?
Usually not. Most lesions are benign, but rapidly growing, painful or hard masses need faster assessment to exclude sarcoma or malignant nerve sheath change.
Do all nerve sheath tumours need surgery?
No. Some can be observed if small, stable and not causing troublesome symptoms. Surgery is more likely if there is pain, growth, neurological deficit, diagnostic uncertainty or concern about malignancy.
Is biopsy always needed before surgery?
No. If sarcoma is suspected, biopsy should be planned through a specialist pathway. If the lesion looks like a benign intraneural tumour managed by a specialist peripheral nerve surgeon, direct excision may be more appropriate.
Will my pain improve after surgery?
Often yes, particularly if pain is caused by pressure from the tumour. In one specialist series, symptoms improved directly after surgery in almost nine out of ten interventions.
Do multiple tumours mean a genetic condition?
Not always, but multiple nerve sheath tumours should prompt consideration of NF1, NF2-related schwannomatosis or schwannomatosis, and sometimes genetics referral.
How long does recovery take?
Many patients go home the same day or next day. Wound healing is commonly around two weeks, but nerve symptoms and scar comfort can keep improving for weeks to months.
"Your treatment plan should be based on which nerve is involved, what symptoms you have now, what function is at risk, and whether monitoring may be safer than surgery." — Mr Ashley Simpson
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