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schwannoma (neurilemoma, neurinoma)
Epidemiology:
1) 7% of primary intracranial neoplasms
2) 29% of primary spinal nerve root tumors [3]
3) rare central nervous system schwannoma [3]
4) generally occurs in patients 40-50 years of age [2]
Pathology:
1) may arise from any cranial, spinal or peripheral nerve
2) commonly involves
a) cranial nerve VIII (most common)
1] arise from vestibular division of nerve
2] enlarging vestibular tumors may compress the cerebellum, pons or facial nerve (CN VII)
b) cranial nerve V
c) dorsal root of spinal nerves (seen in patients with neurofibromatosis type I)
3) bilateral acoustic schwannomas are the hallmark of neurofibromatosis type II
4) corresponds to WHO grade I
Microscopic Pathology:
1) encapsulated sometimes cystic tumor composed of spindle-shaped Schwann cells
2) histopathology:
a) variants: cellular, plexiform, melanotic, epithelioid
b) Antoni A pattern: compact areas of elongated cells with pallisading pattern, Verocay bodies
c) Antoni B pattern: less cellular, loosely textured
d) clusters of lipid laden cells
e) large atypical appearing nuclei considered to be degenerative change
f) occasional mitotic figures may be seen
Immunohistochemistry:
- S100: + strong, diffuse, cytoplasmic, nuclear
- EMA: -
- CD34: - in cellular areas, may be seen associated with degenerative areas
- vimentin: +
- CD68: may be + due to high lysosomal content
- keratin (AE1): commonly +
Clinical manifestations:
1) progressive unilateral hearing loss
2) symptoms from compression of CN VII, pons, cerebellum
Special laboratory:
1) audiometry
2) brainstem auditory evoked potential
Radiology:
-> magnetic resonance imaging (MRI)
a) dense, uniformly enhancing lesions
b) vestibular schwannomas enlarge in the internal auditory canal*
* distinguishing feature from other cerebellar-pontine angle masses
Management:
1) surgical excision
- generally possible to preserve hearing
2) stereotactic radiation therapy with gamma-knife
3) prognosis:
a) schwannomas are clinically benign
b) rarely limits life expectancy [2]
Related
facial nerve (CN VII)
gamma knife radiosurgery (stereotactic radiosurgery)
neurofibromatosis (central) type 2
neurofibromatosis (classic) type 1
neuroma
trigeminal nerve (CN V)
Specific
vestibular schwannoma (acoustic neuroma)
General
nerve sheath tumor
References
- Harrison's Online, Chapter 370, McGraw-Hill, 2002
- Medical Knowledge Self Assessment Program (MKSAP) 16
American College of Physicians, Philadelphia 2012
- WHO Classification of Tumours of the Central Nervous System
Louis DN et al (editors)
IARC Press, 2007, ISBN 978-92-832-2430-2
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