Dysembryoplastic neuroepithelial tumor (DNET)

Case contributed by Assoc Prof Frank Gaillard



Patient Data

Age: 20 years
Gender: Female

A right-sided anteromedial temporal subcortical cystic lesion is present with punctuate enhancing nodule. It is surrounded by a small amount of increased T2 signal and a high FLAIR signal "rim". 

Conclusion: features are most consistent with a low grade localized tumor most likely a DNET.

Case Discussion

The patient went on to have a resection. 


Sections of the brain contain a biphasic tumor composed of atypical neurons and astrocytes. The astrocytic component in areas is lobulated with loose 'myxoid' neuropil containing increased numbers of vessels with increased numbers of astrocytes. The astrocytes show mild to moderate nuclear pleomorphism, with nuclear hyperchromatism and irregular nuclear outlines. Other areas show increased numbers of neurons scattered in the cortex, displaying crowding and inappropriate architectural arrangement. These neurons are enlarged with plump rounded nuclei taking up most of the volume of the cells. Necrosis and microvascular proliferation is not seen.

The abnormal cells are negative for IDH1 by immunohistochemistry and show normal staining pattern for p16 and p53. Staining for ATRX is retained. The cells are negative for BRAF V600E. Ki 67 is <1%.

FINAL DIAGNOSIS: Dysembryoplastic neuroepithelial tumor (DNET)

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