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dermal nerve sheath myxoma

ICD-O:9562/0

Monday 23 May 2016

PO

Definition : Cutaenous benign tumor derived from Schwann cells (peripheral nerve sheath) but without the characteristic features of conventional schwannoma. It is probably a myxoid variant of schwannoma.

Images

- Nerve sheath myxoma

Synopsis

-benign tumor with Schwannian differentiation
- multilobulated and myxoid without the characteristic features of conventional schwannoma
- diffuse S100+ positivity is key to distinguishing it from neurothekeoma
- Unencapsulated multilobulated tumor occupying dermis or subcutis
-well circumscribed myxoid lobules with fibrous rims
- neoplastic cells are small and may be spindled, stellate, epithelioid and ring shaped (often with cytoplasmic nuclear invaginations)
- mild nuclear atypia
- rare or no mitotic figures
- scant eosinophilic cytoplasm envelops small round nuclei, with thin bipolar or multipolar (spider-like) processes
- cellular interconnections are common so cord-like, nested and syncytial arrangements may develop
- possible hyperplastic and hyperpigmented epidermal reaction

Differential diagnosis

- neurothekeoma (especially myxoid and mixed variants)
- plexiform neurofibroma
- myxoid schwannoma
- cutaneous myoepithelioma
- superficial acral fibromyxoma (digital fibromyxoma)
- cutaneous myxoma / superficial angiomyxoma
- dermal mucinoses

See also

- nerve sheath tumors

- myxoid tumors