Ovary

Other tumors

PNET / Ewing sarcoma



Topic Completed: 1 December 2014

Minor changes: 28 June 2021

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

PubMed Search: Peripheral primitive neuroectodermal tumor [title] ovary

Nalini Gupta, M.D.
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Cite this page: Gupta N. PNET / Ewing sarcoma. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/ovarytumorPNET.html. Accessed October 21st, 2021.
Definition / general
  • Neuroectodermal tumors of ovary classified into 3 types: well, moderate and poorly differentiated
  • PNET is poorly differentiated NET of ovary
  • PNET is monophasic teratoma of ovary composed exclusively of neuroectodermal element
  • Most common of all neuroectodermal ovarian tumors
  • Morphologically resembles PNET of brain, also called 'central' PNET
  • Aggressive tumors treated by chemotherapy and surgery
Epidemiology
  • Young women 10 - 30 years
Sites
  • Most common in kidney; also bone and soft tissue
Clinical features
  • Abdominal / pelvic pain
Diagnosis
  • Final diagnosis is confirmed by IHC
Radiology description
  • USG: solid ovarian mass
Prognostic factors
Case reports
Treatment
  • Surgery, radiation therapy, multiagent chemotherapy, or combination
  • Chemotherapy is with vincristine, doxorubicin, cyclophosphamide and more recently ifosfamide and etoposide (Korean J Obstet Gynecol 2012;55:777)
Clinical images

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MRI and
positron emission
tomography

Gross description
  • Large solid friable tumor with gray-white cut surface
Gross images

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Ovarian cyst

Microscopic (histologic) description
  • Solid nests and sheets of monotonous, primitive and small round cells
  • Numerous mitotic figures
  • Rosettes with central lumen, neuroblastic rosettes, neuropil or foci of glial differentiation present
Microscopic (histologic) images

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Main tumor - teratoma, H&E

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Nodular focus of PNET, H&E

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Fibrous bands and rosettes - kidney, H&E

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H&E, vimentin, synaptophysin, CD99 (fig 1)


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CD99+, kidney

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LCA-, NSE-

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Strong immunoreactivity for CD99

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Immunoreactivity for CD99, vimentin, and CK5 markers

Positive stains
Negative stains
Molecular / cytogenetics description
  • t(11;22)(q24;q12), EWS-FLI1 chimeric RNA
  • Overexpression of N-myc and EGFR
  • Underexpression of Rb and ARHI
Differential diagnosis
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