Dysembryoplastic neuroepithelial tumor

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: ; Sujit Routray, M.D. [2]; Maria Fernanda Villarreal, M.D. [3]

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 tumours 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

• Dysembryoplastic neuroepithelial tumor was first discovered by Dumas-Duport in 1988.

Classification

According to the World Health Organization, dysembryonic neuroepithelial tumors are classified as benign brain tumors (WHO Grade I). Dysembryoplastic neuroepithelial tumors may be classified into 3 groups:

• Complex
  • Specific glioneuronal element (SGNE)
  • Glial nodules and a multinodular architecture
  • Component of associated focal cortical dysplasia is common (Blumcke classification IIIb)
• Simple
  • Specific glioneuronal element (SGNE) only
• Nonspecific
  • 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 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 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 immunohistochemistry, characteristic findings of dysembryoplastic neuroepithelial tumor 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 are 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

• Prognosis is generally good, and 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 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 amount of proteinaceous material or presence of blood products
• Peritumoral FLAIR/T2 oedema is distinctly uncommon

T2 (GE/SWI)

• Calcified areas (common) will show blooming signal loss
• On CT, findings of dysembryoplastic neuroepithelial tumor, 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 and markers.
• Findings on EEG may 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

• There are no known primary preventive measures for dysembryoplastic neuroepithelial tumor.
• Once diagnosed and successfully treated, patients with dysembryoplastic neuroepithelial tumor undergo follow-up periodically.
• Follow-up testing may include MRI evaluation, EEG, and neurological exam.