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

(Left) 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. (Right) 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.

(Left) 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. (Right) 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 ſt. The

tumor points toward the

ventricle, and there is no

surrounding edema. (Courtesy

L. Loevner, MD.)

Brain: Pathology-Based Diagnoses: Neoplasms,

Cysts, and Disorders

140