DYSEMBRYOPLASTIC NEUROEPITHELIAL TUMOR (DNET)
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DNET is a benign, mixed glial-neuronal cortical neoplasm of children and young adults with a long history of partial seizures. DNET corresponds to WHO Grade I.
DNET represents 1.2% of all neuroepithelial tumors in patients under age 20 and 0.2% of those aged more than 20 years. The peak incidence is in children and young adults in their second and third decades of life. There is a male predominance. DNET is associated with cortical dysplasia.
DNET may occur is any part of the supratentorial cortex, but has a predilection for the mesial temporal lobe.
Patients with DNET usually present with long-standing drug-resistant partial seizures.
On MRI, DNET may look like macrogyri. About one-third of these lesions enhance, demonstrating a multiple ring pattern. Peri-tumoral edema and mass effect are conspicuously absent.
The glioneuronal component of the tumor is viscous in consistency, and may be associated with multiple firm nodules representing more stromal components.
The hallmark of DNET is the “specific glioneuronal element,” which is characterized by columns formed by bundles of axons lined by small S-100(+) and GFAP(-) oligodendroglia-like cells oriented perpendicularly to the cortical surface. Between these columns, neurons with normal cytology appear to float in a pale, eosinophilic matrix with scattered GFAP(+) stellate astrocytes.
DNET may occur in patient with neurofibromatosis type I. The molecular genetics of spontaneous DNET have not been elucidated.
DNET is a benign lesion. Long-term tumor control is the norm even following partial surgical resection.