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Dysembryoplastic Neuroepithelial Tumor (DNET)


KEY FACTS

Terminology

  • Dysembryoplastic neuroepithelial tumor (DNET)

    • Benign mixed glial-neuronal neoplasm

    • Frequently associated with cortical dysplasia

Imaging

  • May occur in any region of supratentorial cortex

    • Temporal lobe most common, followed by frontal lobe

    • Mass frequently “points” toward ventricle

  • Sharply demarcated, wedge-shaped

    • Cystic (“bubbly”) intracortical mass

    • Minimal/no mass effect

    • No surrounding edema

  • Slow growth over years

  • Usually does not enhance

  • Faint focal punctate or ring enhancement in 20-30%

    • Higher rate of recurrence if enhancement

Top Differential Diagnoses

  • Focal cortical dysplasia type II (Taylor type)

  • Neuroepithelial cyst

  • Ganglioglioma

  • Pleomorphic xanthoastrocytoma

  • Angiocentric glioma

Pathology

  • WHO grade I

  • Hallmark = specific glioneuronal element

Clinical Issues

  • Longstanding drug-resistant partial complex seizures in child/young adult

  • Surgical resection usually curative

  • Histology usually remains benign even if tumor recurs, enhances

Coronal oblique graphic shows typical appearance of a cystic cortical dysembryoplastic neuroepithelial tumor (DNET), which present in children or young adults with seizures. The gyrus is expanded by the multicystic tumor
; cortical dysplasia
is common in adjacent brain.

Sagittal T1 MR in a young adult with seizures shows characteristic “bubbly” appearance of DNET (WHO grade I neoplasm). Note low T1 signal within the wedge-shaped cortical mass
; there's excellent prognosis with surgical resection.

Axial T2WI MR shows a multilobular, wedge-shaped cystic cortically based mass
in the right posterior frontal lobe. Note the lack of edema and mass effect, given the size of the tumor, which is typical of a DNET.

Axial FLAIR MR in the same patient shows the characteristic appearance of a DNET. Note the cortically based, sharply demarcated, wedge-shaped mass with a hyperintense rim
. The tumor points toward the ventricle, and there is no surrounding edema.

(Courtesy L. Loevner, MD.)

TERMINOLOGY

Abbreviations

  • Dysembryoplastic neuroepithelial tumor (DNET)

Synonyms

  • Mixed glial-neuronal neoplasm

Definitions

  • Benign, highly epileptogenic tumor frequently associated with cortical dysplasia

IMAGING

General Features

  • Best diagnostic clue

    • Demarcated, wedge-shaped/ovoid, cystic/multicystic cortical mass in young patients with longstanding partial complex seizures

  • Location

    • May occur in any region of supratentorial cortex

      • –

        Temporal lobe is most common (45-68%)

        • □

          Often amygdala/hippocampus

      • –

        Frontal lobe is also common (1/3 of cases)

      • –

        Basal ganglia, septum pellucidum are less frequent sites

    • Cortical mass frequently “points” toward ventricle

  • Size

    • Variable: Small (involving part of gyrus)

    • Large (several cm) lesions involving large portion of lobe have been reported

  • Morphology

    • Circumscribed, wedge shaped, cystic

    • Minimal or no mass effect relative to size of lesion

    • No associated surrounding edema

    • Slow growth over many years

      • –

        May remodel overlying bone

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