Dysembryoplastic Neuroepithelial Tumor
Definition: Dysembryoplastic neuroepithelial tumor (DNET) is a benign, mixed glioneuronal neoplasm affecting pediatric and young adult age groups and predominantly involving the cortical location with multinodular architecture composed of columns of axonal bundles oriented perpendicularly to the cortical surface. Seizure is the most common presenting symptom.
Epidemiology: This tumor accounts for 1.2% of all primary intracranial neuroepithelial tumors in patients aged <20 years and for 0.2% in patients aged >20 years.
Molecular and genetic profile: BRAF V600E mutations have been seen in up to 30% of all DNETs and associated with activation of mTOR signaling pathway. Rare association with neurofibromatosis type 1 or XYY syndrome has been noticed.
Clinical features and standard therapy: Gross total resection ensures favorable prognosis, but subtotal resection can lead to slow recurrence and malignant transformation in very rare instances, especially after radiation therapy or chemotherapy.
Ganglioglioma
Definition: Ganglioglioma is a slow-growing, low-grade glioneuronal neoplasm composed of dysplastic and cytologically atypical ganglion cells, with predilection for temporal lobes.
Epidemiology: Less than 2% of all primary central nervous system (CNS) tumors, ganglioglioma primarily affects children and young adults, mostly in the age range of 8.5 to 25 years, with a slight male predominance (˜52%).
Molecular and genetic profile: Up to 60% of gangliogliomas have BRAF V600E mutations and one third show gain of chromosome 7.
Clinical features and standard therapy: Surgery is the first line of therapy and gross total resection ensures favorable prognosis, but recurrence is not uncommon in the setting of subtotal resection. Anaplastic ganglioglioma may require adjuvant radiation therapy and chemotherapy.
Desmoplastic Infantile Astrocytoma and Ganglioglioma
Definition: Desmoplastic infantile astrocytoma and ganglioglioma are low-grade and rare neuroepithelial tumors of infancy composed of neoplastic astrocytes without or with mature neuronal components, including ganglion cells in a background of prominent desmoplastic stroma. These tumors have previously been described by a variety of names, including “superficial cerebral astrocytomas attached to dura” and “desmoplastic supratentorial neuroepithelial tumors of infancy with divergent differentiation.” Desmoplastic infantile astrocytoma (DIA) refers to tumor cells composed of neoplastic astrocytes without neuronal component, and desmoplastic infantile ganglioglioma (DIG) refers to tumor cells composed of both neoplastic astrocytes and mature neoplastic neuronal cells. DIA and DIG are considered a single molecular genetic entity with a spectrum of histological features and are placed in the same category in the current WHO classification of CNS tumors.
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