Dysembryoplastic neuroepithelial tumor
Synonyms and keywords: DNT; DNET; Dysembryoplastic neuroepithelial tumors; Dysembryoplastic neuroepithelial tumour; Dysembryoplastic neuroepithelial tumours

# Overview
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.

# Historical Perspective
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. 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

# Classification
Dysembryonic neuroepithelial tumors are classified as benign brain tumors (WHO Grade I). Dysembryoplastic neuroepithelial tumors may be classified into 3 groups:
- Simple
Specific glioneuronal element (SGNE) only
- 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)
- 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)

# Pathophysiology

## Pathogenesis
The pathogenesis of dysembryoplastic neuroepithelial tumor is characterized by the overgrowth of glioneuronal tissue, which primarily consists of oligodendrocytes. 

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

## Gross Pathology
On gross pathology, characteristic findings of dysembryoplastic neuroepithelial tumor may appear as a cortical mass.

## Microscopic Pathology
- On microscopic histopathological analysis, characteristic findings of dysembryoplastic neuroepithelial tumor may include:
- 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:
- Positive MAP2
- Positive CD34
- Positive calbindin
- Positive nestin
- Positive MIB-1 (Ki-67)
- Positive synaptophysin
- Positive neuron-specific enolase

# Causes
There are no established causes for dysembryoplastic neuroepithelial tumor.

# Differentiating Dysembryoplastic Neuroepithelial Tumor from Other Diseases
Dysembryoplastic neuroepithelial tumor must be differentiated from other tumors that cause seizures, such as:
- Pleomorphic xanthoastrocytoma
- Ganglioglioma
- Oligodendroglioma
- Desmoplastic infantile ganglioglioma

# Epidemiology and Demographics

## Prevalence
The prevalence of dysembryoplastic neuroepithelial tumor remains unknown.

## Age
Dysembryoplastic neuroepithelial tumor is more commonly observed among patients aged between 8 and 19 years old.

## Gender
Dysembryoplastic neuroepithelial tumor affects men and women equally.

## Race
There is no racial predilection for dysembryoplastic neuroepithelial tumor.

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

# Natural History, Complications and Prognosis

## Natural History
- 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.

## Complications
Common complications of dysembryoplastic neuroepithelial tumor include:
- Status epilepticus
- Severe memory loss

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

# Diagnosis

## Symptoms
The most common symptom of dysembryoplastic neuroepithelial tumors are seizures. Other common symptoms of dysembryoplastic neuroepithelial tumor may include:
- Irritability
- Changes in speech
- Difficulty reading or concentrating
- Drowsiness

## Physical Examination
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

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

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

### MRI Findings
On MRI, findings of dysembryoplastic neuroepithelial tumor may include: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

### CT Findings
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

## Other Diagnostic Studies
Dysembryoplastic neuroepithelial tumor may also be diagnosed using EEG. Findings in favor of dysembryoplastic neuroepithelial tumor on EEG include:
- Repetitive spikes
- Burst of polyspikes

# Treatment

## Medical Therapy
There is no treatment for dysembryoplastic neuroepithelial tumor; the mainstay of therapy is surgery.

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

## Prevention

### Primary Prevention
There are no known primary preventive measures for dysembryoplastic neuroepithelial tumor.

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