Dysembryoplastic neuroepithelial tumor

Dysembryoplastic neuroepithelial tumor (also known as DNT or DNET) is a type of benign glioneuronal brain tumor that arises from the oligodendrocyte, which is normally involved in the production of myelin in the central nervous system. Dysembryoplastic neuroepithelial tumor is most commonly found in the temporal lobe (supratentorial cortex). Dysembryoplastic neuroepithelial tumor was first discovered by Dumas-Duport in 1988. Dysembryoplastic neuroepithelial tumors are glioneuronal tumors comprised of both glial and neuron cells and often have ties to focal cortical dysplasia. According to the World Health Organization is classified as benign brain tumors (WHO Grade I). Dysembryoplastic neuroepithelial tumors may be classified according to the World Health Organization into 3 groups: complex, simple, and unspecific. Dysembryoplastic neuroepithelial tumor is more commonly observed among patients aged between 8 and 19 years old. The majority of patients with dysembryoplastic neuroepithelial tumor remain asymptomatic and are undiagnosed until they become symptomatic at the time of diagnosis. Early clinical features include seizures, headaches, and personality changes. Common complications of dysembryoplastic neuroepithelial tumor include status epilepticus and severe memory loss. Surgical excision is the most common approach to the treatment of dysembryoplastic neuroepithelial tumor.

In 1988, Dumas-Duport was the first who described dysembryoplastic neuroepithelial tumor. It was primarily identified in autopsies or when the patient was undergoing a brain surgery for another reason. However, these days due to technological progress, it can be identified with imaging techniques during early stages.^[1][2] It was determined to name this tumor as “dysembryoplastic neuroepithelial tumor” due to unique clinicopathological features of this tumor, including:

• Deformity of the overlying skull
• Early onset of seizure
• Presence of focal cortoical dysplasia in the adjacent cortex

Dysembryonic neuroepithelial tumors are classified as benign brain tumors (WHO Grade I). Dysembryoplastic neuroepithelial tumors may be classified into 3 groups:^[3]

• Simple
  • Specific glioneuronal element (SGNE) only
• Nonspecific
• Complex
  • Specific glioneuronal element (SGNE)
  • Glial nodules and a multinodular architecture
  • Component of associated focal cortical dysplasia is common (Blumcke classification IIIb)
  • Same clinical and neuroimaging features as complex DNE
  • No specific glioneuronal element (SGNE)

The pathogenesis of dysembryoplastic neuroepithelial tumor is characterized by the overgrowth of glioneuronal tissue, which primarily consists of oligodendrocytes. ^[4]

The IDH1 gene mutations have been associated with the development of dysembryoplastic neuroepithelial tumor.

On gross pathology, characteristic findings of dysembryoplastic neuroepithelial tumor may appear as a cortical mass.^[5]

• On microscopic histopathological analysis, characteristic findings of dysembryoplastic neuroepithelial tumor may include:^[3][5]

• Axonal columns oriented to the surface
• Floating neurons in eosinophilic matrix
• Lined by cells similar to oligodendrocytes
• Large central nuclei with indentations
• Multiple small nucleoli (common)
• Clear cytoplasm
• Few stellated astrocytes

On immunohistochemical analysis, characteristic findings of dysembryoplastic neuroepithelial tumor may include:^[3]

• Positive MAP2
• Positive CD34
• Positive calbindin
• Positive nestin
• Positive MIB-1 (Ki-67)
• Positive synaptophysin
• Positive neuron-specific enolase

There are no established causes for dysembryoplastic neuroepithelial tumor.

Dysembryoplastic neuroepithelial tumor must be differentiated from other tumors that cause seizures, such as:^[3]

• Pleomorphic xanthoastrocytoma
• Ganglioglioma
• Oligodendroglioma
• Desmoplastic infantile ganglioglioma

The prevalence of dysembryoplastic neuroepithelial tumor remains unknown.

Dysembryoplastic neuroepithelial tumor is more commonly observed among patients aged between 8 and 19 years old.^[3]

Dysembryoplastic neuroepithelial tumor affects men and women equally.

There is no racial predilection for dysembryoplastic neuroepithelial tumor.

There are no associated risk factors in the development of dysembryoplastic neuroepithelial tumor.

• The majority of patients with dysembryoplastic neuroepithelial tumor remain asymptomatic and only become symptomatic at the time of diagnosis.
• Early clinical features include seizures, headaches, and personality changes.
• If left untreated, the majority of patients with dysembryoplastic neuroepithelial tumor may progress to develop severe cognitive dysfunction.

Common complications of dysembryoplastic neuroepithelial tumor include:^[3]

• Status epilepticus
• Severe memory loss

The prognosis of dysembryoplastic neuroepithelial tumor is generally good; the 5-year survival rate of patients with dysembryoplastic neuroepithelial tumor is approximately 80%.

The most common symptom of dysembryoplastic neuroepithelial tumors are seizures. Other common symptoms of dysembryoplastic neuroepithelial tumor may include:^[3]

• Irritability
• Changes in speech
• Difficulty reading or concentrating
• Drowsiness

Patients with dysembryoplastic neuroepithelial tumor are commonly well-appearing. Physical examination may be remarkable for:

• Memory loss
• Aphasia
• Jerking movements
• Convulsions
• Muscle rigidity
• Sensory loss
• Ataxia

There are no specific laboratory findings associated with dysembryoplastic neuroepithelial tumor.

MRI is the imaging modality of choice for dysembryoplastic neuroepithelial tumor.

On MRI, findings of dysembryoplastic neuroepithelial tumor may include:^[6][3]
T1

• Solid component iso- to hypointense

T1 C+ (Gd)

• Solid component variable contrast enhancement

T2

• Hyperintense solid component
• Variable signal in the cystic component depending on quantity proteinaceous material or presence of blood products
• Peri-tumoral FLAIR/T2 edema is distinctly uncommon

T2 (GE/SWI)

• Calcified areas (common) will show blooming signal loss

On CT scan, findings of dysembryoplastic neuroepithelial tumor may include:

• Tumors with cortical location may scallop the inner table of the skull vault (44-60%) but no erosion
• The cranial fossa can be minimally enlarged at times
• Calcification in approximately 30% (more common histologically)
• Low density
• No enhancement

Dysembryoplastic neuroepithelial tumor may also be diagnosed using EEG. Findings in favor of dysembryoplastic neuroepithelial tumor on EEG include:^[3]

• Repetitive spikes
• Burst of polyspikes

There is no treatment for dysembryoplastic neuroepithelial tumor; the mainstay of therapy is surgery.^[3]

Surgery is the mainstay of therapy for dysembryoplastic neuroepithelial tumor. Surgical excision is the most common approach to the treatment of dysembryoplastic neuroepithelial tumor.

There are no known primary preventive measures for dysembryoplastic neuroepithelial tumor.^[3]

Secondary prevention strategies following diagnosis and treatment of dysembryoplastic neuroepithelial tumor include regular follow-up MRI evaluation, EEG, and neurological exam.

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