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Department of Pathology, University of Oklahoma Health Sciences Center

NeuroTest Question #95 Next question Previous question

Answer: (A) Most of these tumors enhance brightly and homogeneously on MRI. Level of difficulty: 3 NeuroTest NeuroLearn NeuroHelp

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Discussion:

Pathology of the case: On low-magnification, the tumor contains many small, round cells that resemble oligodendroglial cells in a mucoid background. Some large, stellate cells with elongated process and prominent nucleoli are present (Panel A). On high-magnification, the large cells has prominent nuclei and basophilic cytoplasm which resemble neurons (Panel B). An immunohistochemistry for neurofulament cells shows positive immunoreactivity in the large cells but not the small cells (Panel C). These features are typical for a dysembroplastic neuroepithelial tumor (DNET).

Dysembroplastic neuroepithelial tumor (DNET):

Patients usually have a long history of partial complex seizure that starts early in life. In essense, it is practical to see DNET as a ganglioglioma with extensive mucoid changes.
This is a rather rare, very slow growing tumor of WHO grade I. It is always found in a supratentorial location with the mesial temporal lobe as the most common site. Foci of cortical dysplasia can be found in the adjacent brain parenchymal area. They tend to occur in a superficial location. DNETs are hypointense on T1-weighted images and hyperintense on T2-weighted image. They occur as nodular tumor that is cortically based. Their orign from the cortex, however, is better appreciated at the rim of the tumor than the center of the bulk. In some cases, they may look like enlarged gyri. Enhancement is not a constant feature of DNETs.
On surgical resection, the specimen often appear as paste like mucoid material due to its mucoid nature admixed with brain parenchymal fragments.
Histologically, three type of cells, the oligodendroglia-like cells, neurons, and astrocytes, arrange in different patterns. Specific glial neuronal compnent is the histological hallmark of DNETs. They are columns that are perpendicular to the cortical surface and are formed by bundles of axons lined by small oligodendroglia-like cells. In between these columns are pools of mucoid material that are alcian blue positive. Large ganglion cells often float within these muoid pools. Mitosis, pleomophism, necrosis, endothelial proliferation and other signs for aggressive behavior is typically lacking.

Comment: KarMing-Fung@ouhsc.edu