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Schwannoma |
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Clinical Futures |
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Peak age, 30-60 year-old, no sex predilection;
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Most common sites: head, neck, flexor surfaces of the
extremities;
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Associated with NF2, on chromosome 22, that encodes a tumor
suppressor gene, Merlin or
Schwannomin.
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Gross Findings |
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Most are solid, globular masses with the parent nerve embedded
within the fibrous capsule;
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Encapsulated with nodular or smooth surface;
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Cut surface: lobulated , and tan or patchy yellow due to lipid
accumulation;
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May show degenerative changes, including marked lipidization,
cystic changes, hemarrhage and calcification.
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Microscopic Findings |
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Well-formed fibrous capsule;
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Characteristic Antoni A and Antoni B patterns at various
proportions;
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Antoni A: compacted elongate cells with tapered, spindle-shaped
nuclei, variable chromasia, abundant pink or blueish cytoplasm,
and no discernible cell membrane. The cells are aligned and
compactly disposed in broad bundles, interlacing fascicles or
whorls. The Verocay bodies consist of nuclear clusters in
palisaged patterns, in which well-regimented double rows of
nuclei seperated by algined eosinophilic cell processes. The
nuceli are serveral times larger than those in most of
neurofibromas;
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Antoni B: looaw-textured, cobweb meshwork of cells with
multi-polar processes;
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Thickened, hyalinized vessels, with perivascular hemosiderin,
thrombosis or microhemorrhage
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Subtypes |
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Cellular schwannoma: high cellularity, large Antoni A pattern,
and absence of well-formed Verocay bodies;
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Plexiform schwannoma: composed of exclusively Schwann cells and
exhibits plexiform;
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Psammomatous melanotic schwannoma: melanin-producing cells with
features of Schwann cells in EM. S-100 and HMB-45 positive.
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Differential Diagnosis |
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Schwannoma |
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Neurofibroma |
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NF2 association |
NF1 association |
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Commonly in extremities |
Commonly involves trunk |
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Nerve often identified |
Nerve infrequently
identified |
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Eccentric to nerve |
Incorporates nerve |
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Globular |
Globular, fusiform or
diffuse |
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Encapsulated |
No capsule |
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Occasionally cystic |
Noncystic |
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Biphasic, Antoni A and B
patterns |
Uniphasic |
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Axons often absent |
Axons often present |
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Palisading and Verocay
bodies |
No palisading, Wagner-Meissner
or Pacinian-like corpuscles |
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Immunohistochemistry Straining |
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S-100 and vimentin, positive
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GFAP and CD68, patchy positivity
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CD34, only in Antoni B
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Leu-7, variable
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Election Microscopy |
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Prominent arrays of cell processes coated with basal lamina, and the
processes are long, thin, closely packed and intertwined.
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Cytogenetics |
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Reference |
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