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Mediastinum

Other benign / low grade tumors

Schwannoma

Reviewer: Hanni Gulwani, M.D. (see Reviewers page)
Revised: 2 March 2013, last major update December 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
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● Usually in posterior mediastinum, asymptomatic
● Most common mediastinal neurogenic tumor
● May present with symptoms of esophageal or nerve root compression
● Benign

Terminology
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● Also called neurilemoma

Epidemiology
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● Usually in young adults

Case reports
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● 33 year old man with asymptomatic tumor (G Chir 2004;25:35)
● 65 year old man diagnosed by endoscopic ultrasonography-guided fine needle aspiration cytology (Case Rep Gastroenterol 2011;5:411)

Treatment
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● Excision is almost always curative

Gross description
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● Encapsulated and sharply demarcated from adjacent soft tissue
● May appear to “hang” from large nerves
● Usually yellow cut surface, rarely dark red/black due to hemorrhage
● Degenerative changes common (fat, hemorrhage, cysts)

Gross images
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51 year old man

Micro description
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● Biphasic pattern of fusiform cells
● Cellular areas with nuclear pallisading (Antoni A) and Verocay bodies and myxoid areas with only occasional cells (Antoni B)
● Prominent thick walled blood vessels
● No / rare mitotic figures

Micro images
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Antoni A

Antoni B

Ancient change / ancient schwannoma

Micro description
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● Cystic changes, marked nuclear atypia, but no mitotic figures

Electron microscopy description
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● Neural differentiation with elongated overlapping cell processes
● Primitive junctions may resemble mesaxons
● Abundant pericellular basal lamina

Cellular schwannoma

Micro description
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● Densely cellular with herringbone, storiform or fascicular growth patterns, mild nuclear atypia, brisk mitotic activity, but no necrosis, no atypical mitotic figures

Differential diagnosis
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● MPNST or other sarcoma: atypical mitotic figures, necrosis, not encapsulated

Glandular schwannoma

General
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● Epithelial differentiation is focally present

Melanotic schwannoma

General
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● Pigment present

Psammomatous-melanotic schwannoma

General
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● Psammomatous calcification and pigment are present

End of Mediastinum > Other benign / low grade tumors > Schwannoma

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