Soft tissue
Peripheral nerve tumors
Schwannoma

Author: Vijay Shankar, M.D. (see Authors page)

Revised: 21 September 2016, last major update November 2012

Copyright: (c) 2002-2016, PathologyOutlines.com, Inc.

PubMed Search: Schwannoma [title] soft tissue

See also: ancient, angiosarcoma, cellular, epithelioid, microcystic-reticular, pigmented, plexiform, psammomatous melanotic

Definition / General
  • Also known as neurilemoma
  • Encapsulated biphasic nerve sheath tumor derived from Schwann cells with highly ordered cellular component (Antoni A) that palisades (Verocay bodies), plus myxoid component (Antoni B)
  • Small tumors may be all Antoni A

Malignant transformation:
  • Occurs even without neurofibromatosis, tumors usually have epithelioid features and often areas of benign schwannoma (Am J Surg Pathol 2001;25:13)
  • Transforms to MPNST, angiosarcoma or epithelioid malignant change (EMC)
  • Most common sites are limb, limb girdles, head / neck
  • Schwannoma with MPNST: benign schwannoma with no other primary tumor that may have metastasized to schwannoma, histologically malignant cells resembling epithelioid MPNST; 5 year survival < 20%
Clinical Features
  • Ages 20 - 50; M = F
  • Head, neck, flexor upper and lower extremities, retroperitoneum, posterior spinal roots, cerebellopontine angle
  • Slow growing; no symptoms until becomes large; may wax and wane in size
  • Pain or rapid enlargement of preexisting lesion are suggestive of malignant change
  • May be due to alteration / loss of NF2 gene product
Treatment
  • Excision; recurrence rare, so attempt to preserve nerve if clinically significant
Clinical Images

Images hosted on PathOut servers:

Skin, courtesy of Mark R. Wick, M.D.

Gross Description
  • Usually solitary
  • Large tumors may be cystic
  • Nerve of origin present in periphery - does not penetrate substance of tumor
  • Dumbbell tumor: in posterior mediastinum, originates from or extends into vertebral canal
Gross Images

Images hosted on PathOut servers:

Courtesy of Mark R. Wick, M.D.



Images hosted on other servers:

Well circumscribed

Micro Description
  • Biphasic: compact hypercellular Antoni A areas and myxoid hypocellular Antoni B areas (may be absent in small tumors)
  • Cells are narrow, elongate, wavy with tapered ends interspersed with collagen fibers
  • Nuclear palisading around fibrillary process (Verocay bodies) are often seen in cellular areas
  • Large irregularly spaced vessels are most prominent in Antoni B areas
  • Gaping tortuous lumina have thickened hyalinized walls and may have thrombi
  • Tumor cells have ill defined cytoplasm, dense chromatin
  • May have foamy macrophages
  • Often displays degenerative nuclear atypia (ancient change)
  • Amianthoid fibers or collagenous spherules: large nodular masses of collagen with radiating edges
  • Rarely epithelioid, glandular (may be entrapped sweat glands), pigmented, plexiform, rosettes
  • Rare mitotic figures, no axons except where nerve is attached
Micro Images

Images hosted on PathOut servers:
Images courtesy of Mark R. Wick, M.D.:

Verocay bodies



GFAP



Images hosted on other servers:

Various images



Positive Stains
Negative Stains
Electron Microscopy Description
  • Elongated cells with continuous basal lamina, thin cytoplasmic processes, aggregates of intracytoplasmic microfibrils, peculiar intracytoplasmic lamellar bodies, extracellular long-spacing collagen
  • Contains lipid
  • Has characteristic luse bodies (long spaced collagen)
Differential Diagnosis