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schwannoma

Monday 8 March 2004

schwannomas; neurilemmoma

Digital slides

- UI:345 - Schwannoma.
- JRC:4740 : Neurilemoma (Schwannoma).
- JRC:4741 : Neurilemoma (Schwannoma) - Bone, Mandible.
- JRC:8409 : Neurilemoma (Schwannoma).
- JRC:8410 : Neurilemoma (Schwannoma).
- JRC:8411 : Neurilemoma (Schwannoma) (VIII nerve).
- JRC:8414 : Neurilemoma (Schwannoma) - Submucosal, palate.
- JRC:8417 : Neurilemoma (Schwannoma).
- JRC:8423 : Neurilemoma (Schwannoma).
- JRC:8748 : Neurilemoma (Schwannoma) - Tongue, mucosal.
- JRC:10003 : Neurilemoma (Schwannoma) - Peritoneum - retroperitoneum.
- JRC:12065 : Neurilemoma (Schwannoma) - Soft tissues.
- JRC:12067 : Neurilemoma (Schwannoma) - Soft tissues.
- JRC:13972 : Neurilemoma (Schwannoma): Cellular & plexiform nodular - CNS.
- JRC:1295 : Neurilemoma (Schwannoma) - Salivary glands, parotid. (+)
- JRC:14800 : Neurilemoma (Schwannoma) - Adrenal.

"Ancient" features
- JRC:3076 : Schwannoma with degenerative changes ("ancient schwannoma").
- JRC:14599 : Schwannoma with degenerative changes ("ancient features").
- JRC:397 : Ancient schwannoma with bizarre giant cells - Peritoneum (pelvis)
- JRC:14737 : Schwannoma with degenerative changes ("ancient features").

Cellular schwannoma
- JRC:357 : Cellular Schwannoma - Retroperitoneum.
- JRC:96 : Cellular Schwannoma - Groin.
- JRC:14942 : Cellular Schwannoma - Peritoneum (retroperitoenum).
- JRC:485 : Cellular Schwannoma - Peritoneum.
- JRC:15245 : Cellular Schwannoma - Peritoneum.

Melanocytic schwannoma
- JRC:19089 : Pigmented (melanocytic) Schwannoma of stomach.

Definition: Schwannomas are benign peripheral nerve sheath tumors believed to be composed purely of cells with ultrastructural features of Schwann cells.

Schwannomas are believed to develop eccentrically from the surface of nerves and not to contain axons, other than immediately beneath the capsule. This concept has recently been disputed in cases associated with neurofibromatosis type 2 (NF2).

Cutaneous schwannomas (neurilemmomas) are uncommon, slow-growing, usually solitary tumors with a propensity for the limbs of adults.

Pain, tenderness, and paresthesiae may be present in up to one-third of lesions.

They measure 2–4 cm in diameter.

They are of Schwann cell origin.

Multiple tumors are uncommon and can occur in several clinical settings: in association with neurofibromas in von Recklinghausen’s disease; or as multiple, localized tumors which may be a distinct disease; in neurofibromatosis type 2 (NF-2 – MIM.101000), due to mutations in the NF2 gene, located at 22q12.2, and characterized by vestibular schwannomas and other tumors; and in (familial) schwannomatosis (MIM.162091), characterized by the development of multiple spinal, cranial and peripheral schwannomas in the absence of a vestibular schwannoma

Schwannomas are circumscribed encapsulated tumors, usually confined to the subcutis. The nerve of origin may sometimes be seen along one border.

The agminate tumors and some of those in schwannomatosis are often situated in the dermis.

Multiple small tumor nodules may be present in these forms, as well as hypertrophied peripheral nerves. The term ‘plexiform schwannoma’ has been applied to this type.

It originates from nerve sheath.

Variants

- cellular schwannoma
- plexiform schwannoma (and extensive plexiform schwannoma)
- epithelioid schwannoma
- deep-seated plexiform schwannoma
- neuroblastoma-like schwannoma
- melanotic schwannoma
- psammomatous melanotic schwannoma
- pseudoglandular schwannoma
- Wagner–Meissner schwannoma
- ‘congenital neural hamartoma’ (or fascicular schwannoma)

Immunochemistry

- S-100 +

- neurofilament + (NF)

  • NF-positive axons in conventional schwannomas (55%) and cellular schwannomas (75%) (17721192)

Immunoperoxidase methods demonstrate S100 protein,vimentin, SOX 10,and myelin basic proteinin the tumor cells.

Glial fibrillary acidic protein (GFAP) is present in a small number of cases.

Epithelial membrane antigen is found in the perineurial cells in the capsule of schwannomas, as in that of solitary neuromas.

The conventional view has been that schwannomas, unlike neurofibromas, do not possess intratumoral axons. However, a recent study using an antibody to neurofilament protein found axons in 30–70% of schwannomas, the incidence varying with the histological subtype.

All types of Schwann-cell-derived tumors express the DNA-binding transcription factor, activating protein 2 (AP-2), mainly in their nucleus.

Differential diagnosis

- neurofibroma

  • The usual presence of intratumoral axons in neurofibromas is said to allow easy distinction from schwannomas.
  • The frequent presence of intratumoral axons in schwannomas argues against conventional views of these lesions’ pathogenesis as an eccentric encapsulated lesion and raises the possibility that a more diverse cell population, perhaps more closely resembling neurofibromas, may constitute these neoplasms. (17721192)
  • Although NFP-positive axons were most often present in the conventional and cellular variants of schwannoma, their presence was also observed in a minority of ancient, gastric and plexiform schwannomas. (17721192)
  • Differentiation between neurofibroma and schwannoma in cases with overlapping cytoarchitectural features should not be based solely on the presence or absence of NFP-positive axons within a given tumor. (17721192)

Electron microscopy

There are aggregates of mature Schwann cells with thin, complexly entangled cytoplasmic processes, but only rare cell junctions. One report suggested that the Antoni B areas showed features of degeneration, but this finding has not been confirmed by others.

Gene mutations

- somatic mutations or deletions of NF2

See also

- nervous tumors

  • schwannian tumors

Portfolio

  • Section of a schwannoma
  • Schwannoma
  • Intradural extramedullary schwannoma
  • Intradural extramedullary schwannoma
  • Cellular schwannoma
  • Cellular schwannoma
  • Cellular schwannoma