Mediastinum
Soft tissue tumors
Other soft tissue tumors


Topic Completed: 1 December 2012

Minor changes: 19 March 2021

Copyright: 2003-2021, PathologyOutlines.com, Inc.

PubMed Search: Lipoma[TI] mediastinum, Liposarcoma mediastinum[TI], Malignant peripheral nerve sheath tumor[TI] mediastinum, Schwannoma[TI] mediastinum

Hanni Gulwani, M.B.B.S.
Page views in 2021 to date: 89
Cite this page: Gulwani H. Other soft tissue tumors. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/mediastinumothersofttissuetumors.html. Accessed May 15th, 2021.
Lipoma

Definition / general
  • Common, occur throughout mediastinum
  • Often very large and located just above diaphragm
  • Anterosuperior lipomas clinically resemble thymolipoma

Case reports

Microscopic (histologic) images

Images hosted on other servers:

Necrotic adipocytes
(circle) and peripheral
histiocytic reaction
(arrow)



Differential diagnosis
Liposarcoma

Diagrams / tables

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Clinicopathologic features of childhood cases



Clinical features
  • Rare in mediastinum; age range of 3 - 72 years
  • More common in anterior / posterior than superior mediastinum
  • Well circumscribed multinodular masses, 2 - 61 cm
  • Most common subtypes: well differentiated, dedifferentiated, pleomorphic (myxoid uncommon, Am J Surg Pathol 2007;31:1868)
  • Mediastinum shows a preponderance of uncommon subtypes and unusual morphologic variants; correct classification has important implications, with most patients with well differentiated / dedifferentiated liposarcoma having a protracted clinical course, in contrast to the more rapid disease progression seen in patients with myxoid and pleomorphic liposarcoma (Am J Surg Pathol 2012;36:1395)
  • Associated with liposarcoma of thigh or retroperitoneum as a multicentric tumor
  • Lipoleiomyosaroma: well differentiated liposarcoma with leiomyosarcomatous differentiation (Am J Surg Pathol 2002;26:742)

Case reports

Microscopic (histologic) images

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Various patterns

Malignant peripheral nerve sheath tumor

Clinical features
  • Often associated with neurofibromatosis
  • 4% of MPNST show perineurial cell differentiation (Am J Surg Pathol 1998;22:1368)
  • Often spreads to pleura or lungs

Prognostic factors
  • Extremely poor prognosis if glandular or rhabdomyosarcomatous features

Case reports

Gross description
  • Unencapsulated, degenerative changes common (fat, hemorrhage, cysts)

Microscopic (histologic) description
  • Bizarre cells and tumor giant cells
  • Also atypical mitotic figures and necrosis
  • May have areas of uniform bland spindle cells
  • Rarely has rhabdomyosarcomatous features ("triton tumor") or glandular differentiation

Microscopic (histologic) images

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Low grade tumor has
increased cellularity,
nuclear atypia, scattered
mitotic figures

Fascicular proliferation of atypical spindle cells

Schwannoma

Definition / general
  • Usually in posterior mediastinum, asymptomatic
  • Most common mediastinal neurogenic tumor
  • May present with symptoms of esophageal or nerve root compression
  • Benign

Terminology
  • Also called neurilemoma

Epidemiology
  • Usually in young adults

Case reports

Treatment
  • Excision is almost always curative

Gross description
  • 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



Microscopic (histologic) description
  • 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
  • Ancient change: cystic changes, marked nuclear atypia but no mitotic figures
  • Cellular: densely cellular with herringbone, storiform or fascicular growth patterns, mild nuclear atypia, brisk mitotic activity but no necrosis, no atypical mitotic figures (unlike MPNST or other sarcomas)
  • Glandular: epithelial differentiation is focally present
  • Melanotic: pigment present
  • Psammomatous-melanotic: psammomatous calcification and pigment are present

Microscopic (histologic) images

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Antoni A

Antoni B



Electron microscopy description
  • Ancient change / ancient schwannoma:
    • Neural differentiation with elongated overlapping cell processes
    • Primitive junctions may resemble mesaxons
    • Abundant pericellular basal lamina
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