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Benign · Nerve sheathPainful nodule DDxMPNST red flags

Neurofibroma, schwannoma and traumatic neuroma

Solitary neurofibroma; cutaneous neurofibroma; schwannoma; neurilemmoma; traumatic neuroma; amputation neuroma; stump neuroma

Neurofibroma, schwannoma and traumatic neuroma are benign peripheral nerve or nerve-sheath lesions that enter skin-oncology practice as solitary dermal nodules, painful nodules or lesions arising in scars and amputation stumps. Most are benign and manageable with observation or planned excision, but the red-flag context matters: rapid growth, persistent or escalating pain, neurological deficit, deep fixation, size increase in a plexiform neurofibroma or known NF1 should raise concern for malignant peripheral nerve sheath tumour and prompt imaging/MDT referral rather than casual excision.

CurrentLast reviewed 5 June 2026

Neurofibroma

  • Solitary cutaneous neurofibroma is a soft, skin-coloured to pink or brown papule/nodule and may invaginate with pressure (“buttonhole” sign).
  • Multiple neurofibromas, plexiform neurofibroma, café-au-lait macules and axillary/inguinal freckling should trigger assessment for NF1 or related syndromes.
  • Histology shows a non-encapsulated proliferation of Schwann cells, fibroblasts, perineurial-like cells and mast cells in a myxoid collagenous stroma.
  • Solitary superficial lesions are benign; plexiform neurofibromas in NF1 carry malignant-transformation risk.
  • Cosmetic or symptomatic solitary lesions can be excised, but diffuse/plexiform lesions need specialist planning.

Schwannoma

  • Schwannoma is a benign, encapsulated nerve-sheath tumour that is usually eccentric to the parent nerve rather than infiltrating it.
  • Clinically it may be a slow-growing subcutaneous nodule with pain, paraesthesia or a positive Tinel sign when tapped.
  • Histology classically shows Antoni A and Antoni B areas, Verocay bodies and strong S100/SOX10 staining.
  • Surgery aims to shell out/enucleate the tumour while preserving the parent nerve when feasible.
  • Multiple schwannomas suggest schwannomatosis or NF2-related schwannomatosis rather than ordinary solitary disease.

Traumatic neuroma

  • Traumatic neuroma is a disorganised reactive proliferation at the end of an injured nerve rather than a true neoplasm.
  • It presents as a tender or electric-shock-like nodule in a scar, amputation stump, biopsy site or surgical field.
  • Pain may be provoked by pressure, tapping or movement; symptoms can be disproportionate to visible skin change.
  • Histology shows haphazard nerve fascicles embedded in fibrous scar tissue.
  • Management ranges from reassurance and desensitisation to local anaesthetic blocks, neuropathic analgesia or planned excision/nerve handling for persistent severe symptoms.

Red flags for malignancy

  • Rapid increase in size, especially in a known plexiform neurofibroma or NF1 patient.
  • New, persistent, nocturnal or escalating pain rather than stable mild tenderness.
  • New neurological deficit, paraesthesia, weakness or loss of function in the nerve distribution.
  • Deep location, fixation, size greater than expected for a superficial lesion or a mass over 5 cm.
  • Red flags should prompt MRI and sarcoma/skin-cancer MDT discussion; avoid unplanned marginal excision of a suspected MPNST.

Practical approach

  • For a small, stable, superficial solitary lesion with benign clinical features, observation or elective excision with histology is reasonable.
  • For painful nodules, establish whether pain is neuropathic, vascular, smooth-muscle-related, inflammatory or malignant-red-flag pain.
  • Ask about personal/family history of NF1, multiple nerve-sheath tumours, café-au-lait macules, freckling and previous radiotherapy.
  • Use ultrasound for superficial lesion characterisation when helpful, but MRI is preferred for deep nerve-sheath tumours or malignant concern.
  • Communicate nerve-related symptoms to pathology and radiology; the clinical context changes the differential diagnosis.

References

  1. DermNet. Solitary neurofibroma.
  2. Johns Hopkins Medicine. Schwannoma.
  3. Yao C et al. Traumatic neuromas of peripheral nerves: diagnosis, management and future perspectives. Front Neurol. 2023;13:1039529.
  4. Farid M et al. Malignant peripheral nerve sheath tumors. Oncologist. 2014.

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