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.
Figure 17.1. Imaging of DNET, right temporal lobe. A. Axial CT unenhanced: Low-density lesion in the right posterior hippocampus. B. Axial fluid-attenuated inversion recovery (FLAIR): Heterogeneously hyperintense lesion.
Figure 17.1. (continued) C. Sagittal FLAIR: Heterogeneously hyperintense lesion. D. Axial T1 precontrast: Hypointense lesion. E. Axial T1 postcontrast: Small focal area of enhancement within the lesion. F. Axial T1 postcontrast: Small focal area of enhancement within the lesion. G. Axial T2: Hyperintense lesion. H. Axial diffusion-weighted imaging (DWI): Hypointense lesion.
Figure 17.1. (continued) I. Axial apparent diffusion coefficient (ADC): No reduced diffusion within the lesion.
Figure 17.2. Imaging of DNET, left frontal lobe. A-C. Axial T1 precontrast: Heterogeneous hypointense multicystic lesion. D-F. Axial T1 postcontrast: Small focal enhancement in the deep aspect of the lesion.
Figure 17.2. (continued) G-I. Axial T2: “Bubbly” pattern of multicystic hyperintense lesion. J-L. Coronal T1 postcontrast: Small focal enhancement in the deep aspect of the lesion.
Figure 17.2. (continued)
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.
Figure 17.3. Imaging of Ganglioglioma. A-C. Axial CT unenhanced: Heavily calcified right parietal mass with anterior cystic component. D-F. Axial T2: Heterogeneously hypointense mass with anterior cystic component with high-signal intensity.
Figure 17.3. (continued) G-I. Coronal gradient echo: Susceptibility blooming due to calcium and circumscribed superior cystic component. J-L. Axial T1 postcontrast: Peripheral nodular enhancement.
Figure 17.4. Imaging of Gangliogliomas, four different patients, postcontrast T1-weighted Imaging. A-C. Left medial temporal ganglioglioma: Small enhancing nodule in the left medial temporal lobe. D-F. Hypothalamic ganglioglioma: Enhancing nodule in the hypothalamus with inferior extension in the suprasellar cistern and a superior cystic component causing mass effect on the third ventricle.
Figure 17.4. (continued) G-I. Left temporal ganglioglioma: Large cystic and solid nodular mass with mild mass effect but no surrounding edema. J-L. Left occipital anaplastic ganglioglioma: Circumscribed mass with rim enhancement and internal stellate nodule and marked surrounding edema.
Figure 17.5. Imaging of Spinal Ganglioglioma. A. Coronal FLAIR: Expansile hypointense medullary and cervical spinal cord mass. B-C. Sagittal T2: Hyperintense mass with circumscribed cystic component from C4 to C7 levels and central solid tissue at C5-C6. D-F. Sagittal T1 precontrast: Expansile hypointense mass with circumscribed cystic component from C4 to C7 levels and central solid tissue at C5-C6.
Figure 17.5. (continued) G-I. Sagittal T1 postcontrast: Avid peripheral and central enhancement within the circumscribed cystic component. J-L. Axial T1 postcontrast: Thin peripheral and bulky eccentric enhancement.
Figure 17.6. Imaging of Spinal Ganglioglioma, two different patients. A-C. Cervicomedullary ganglioglioma. A. Sagittal T2: Expansile homogeneously hyperintense intramedullary mass. B. Sagittal T1 precontrast: Expansile homogeneously hypointense intramedullary mass. C. Sagittal T1 postcontrast: Avid enhancement. D-F. Lower cervical ganglioglioma. D. Sagittal T2: Long segment multiloculated intramedullary cystic mass with syrinx from C1 to C4. E. Sagittal T1 precontrast: Heterogeneous hypointense mass. F. Sagittal T1 postcontrast: Heterogeneous enhancement of tumor from C5 to T1.
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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