Schwannoma and neurofibromatosis type 2
- Lesion
Schwannomas are benign tumours of Schwann cells that push the nerve aside; two on the hearing nerves mean neurofibromatosis type 2.
What it is
Schwannomas are benign encapsulated tumours of neoplastic Schwann cells that grow on a nerve and displace its axons. Most are sporadic, with loss of the NF2 gene product merlin; they arise on cranial nerve VIII (vestibular schwannoma), spinal roots and peripheral nerves of the limbs. NF2-related schwannomatosis (neurofibromatosis type 2) is an autosomal dominant syndrome with bilateral vestibular schwannomas, meningiomas and spinal ependymomas. Other schwannomatoses involve SMARCB1 or LZTR1 and cause painful multiple schwannomas without vestibular tumours. Other benign nerve sheath tumours include perineurioma, granular cell tumour and hybrid tumours.
Structure
- Gross: firm, tan, encapsulated mass with cystic and yellow areas, attached to but separate from the nerve.
- Antoni A: compact fascicles of spindle cells; rows of nuclei alternate with anuclear zones (Verocay bodies).
- Antoni B: loose, myxoid tissue with microcysts and foamy macrophages.
- Degenerative atypia ('ancient' schwannoma) is not a sign of malignancy.
- Granular cell tumour: cells packed with lysosomal eosinophilic granules, S100 positive, often in the tongue; perineurioma: EMA positive, S100 negative.
Step by step
- Both copies of NF2 (merlin) are lost in a Schwann cell.
- Merlin normally stops growth when cells contact each other (contact inhibition through Hippo signaling).
- Without merlin, Schwann cells proliferate on the nerve surface and form an encapsulated mass.
- The tumour displaces axons to the side rather than surrounding them.
- Growth compresses neighbours, such as the cochlear nerve and brainstem at the cerebellopontine angle.
Schwannoma vs neurofibroma
| Feature | Schwannoma | Neurofibroma |
|---|---|---|
| Relation to nerve | Eccentric, encapsulated, axons pushed aside | Infiltrative, axons run through it |
| Cells | Only neoplastic Schwann cells | Schwann cells plus fibroblasts, perineurial cells, mast cells |
| Pattern | Antoni A and B, Verocay bodies | Wavy nuclei in loose collagen ('shredded carrots') |
| S100 | Diffuse, strong | Patchy |
| Syndrome | NF2, schwannomatosis | NF1 |
| Malignant change | Very rare | Plexiform tumours can become MPNST |
Markers
- S100
- SOX10
- Collagen IV around single cells
- Loss of SMARCB1 in a mosaic pattern (schwannomatosis)
Clinical notes
- Unilateral progressive hearing loss with tinnitus in an adult: MRI to look for vestibular schwannoma.
- Bilateral vestibular schwannomas under 30 define NF2.
- Limb schwannomas cause a painless or tender mass, sometimes with tingling when pressed.
Test yourself
Think of the answer, then tap the question to see it.
What are Verocay bodies?
Rows of palisading nuclei separated by anuclear zones in Antoni A areas of a schwannoma.
Which gene and protein are lost in schwannomas?
NF2, encoding merlin.
What defines NF2?
Bilateral vestibular schwannomas, often with meningiomas and ependymomas.
How do schwannomas relate to the parent nerve?
They are encapsulated and eccentric, pushing axons aside.
Elsewhere in DurgiPedia
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Neurofibromatosis type 2: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2025); Vestibular Schwannoma (StatPearls (NCBI Bookshelf), 2025).
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Representative model, for educational purposes only.