CNS tumor
Neuronal and mixed neuronal - glial tumors
Dysembryoplastic neuroepithelial tumor (DNET)

Author: Eman Abdelzaher, M.D., Ph.D. (see Authors page)

Revised: 31 August 2017, last major update December 2013

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Dysembryoplastic neuroepithelial tumor (DNET)

Cite this page: Abdelzaher, E. Dysembryoplastic neuroepithelial tumor (DNET). PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/cnstumorDNET.html. Accessed October 21st, 2017.
Definition / general
  • Benign mixed glioneuronal neoplasm of children and young adults, characteristically associated with intractable partial seizures
  • Corresponds to WHO grade I
  • First described by Daumas-Duport in 1988 (Neurosurgery 1988;23:545)
  • Incidence:
    • 1.2% of all neuroepithelial tumors diagnosed in patients younger than 20 years (Arq Neuropsiquiatr 1998;56:232)
    • 1 - 19% of surgical resections for epilepsy
  • Age and sex:
    • Children and young adults
    • Usually < 20 years
    • Males are more affected
Sites
  • Supratentorial cerebral cortex (50% temporal lobe)
  • Other sites, e.g. septum pellucidum, basal ganglia, brain stem, cerebellum
Diagrams / tables

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Dysembryoplastic neuroepithelial tumor (DNET)

Clinical features
  • Chronic partial seizures in supratentorial tumors
  • No progressive neurological deficit
Radiology description
  • MRI:
    • Cortical based
    • Hyperintense on T2 "bubbly appearance"
    • No edema or mass effect
    • Enhancement (1/3 of cases): heterogeneous or multiple ring pattern
  • CT:
    • May show calcification, may scallop the inner table of the skull vault
Radiology images

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10 year old girl with seizure

Case reports
Treatment
  • Gross total resection or even subtotal resection usually achieves stabilization and seizure control
Prognosis
  • Benign with excellent prognosis even with subtotal resection
  • Rare recurrence
  • Anaplastic transformation is extremely rare
Gross description
  • Multinodular cortical lesion
  • Soft and gelatinous
Gross images

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Frontobasal surgical specimen

Microscopic (histologic) description
  • Intracortical lesion
  • Uniform oligodendroglioma-like cells in a mucin rich background
  • Hallmark: specific glioneuronal elements (columns formed of axons lined by uniform oligodendroglioma-like cells) with intervening floating neurons (cortical neurons in mucin pools)
  • Scattered astrocytes
  • Cortical dysplasia in adjacent cortex
  • Rare mitotic figures
  • Histological types:
    • Simple form: specific glioneuronal elements only
    • Complex form: glial nodules (imparting the multinodular appearance) with internodular specific glioneuronal elements and adjacent cortical dysplasia
    • Nonspecific form: controversial entity, no specific glioneuronal elements, resembles low grade glioma, diagnosed on clinicoradiological grounds
Microscopic (histologic) images

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Dysembryoplastic neuroepithelial tumor

Variably sized oligodendroglia

Oligodendroglia-like cells


NeurN

Synaptophysin

Neurofilament

Cytology description
  • Oligodendroglioma-like cells
  • Cortical neurons
  • Mucin rich background
  • Floating neurons in clusters or intricate patterns or microcystic
  • Also prominent extracellular mucin
  • Compared to oligodendrogliomas, have larger nuclei, frequent nuclear indentation and multiple small nucleoli (vs. round nuclei with only occasional nucleoli in oligodendrogliomas)
  • Also have eosinophilic granular bodies in background (Acta Cytol 2003;47:624), may have bipolar astrocytes, mild nuclear atypia, microcystic change
  • Adjacent cortex may show cortical dysplasia with disturbed lamination and architectural disarray
  • No / rare necrosis, no / rare endothelial proliferation, uncommon mitotic figures
Cytology images

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Smear preparations

Partially arranged as columnar structures

Fine neuritic processes

Moderately cellular with uniform glial cells

Immunohistochemistry
Electron microscopy description
  • Oligodendroglial-like cells, elongated processes forming a neuropil-like structure and an expanded mucoid extracellular space (Folia Neuropathol 1999;37:167)
Differential diagnosis