Presentation
Seizures.
Patient Data
A high T2 signal lesion involves the cortex of the posterior aspect of the right insula. The lesion incompletely suppresses on FLAIR with a peripheral bright rim persisting. It shows facilitated diffusion. There is no associated contrast enhancement. MR perfusion shows no increase in rCBV. There is no susceptibility blooming in the lesion. The hippocampal formations are normal and symmetrical. No other intracranial lesion. No hydrocephalus.
Expected post-operative findings following resection.
Case Discussion
Although this lesion does not have the classical "bubbly" appearance, it is a T2 hyperintense cortical-based lesion in a patient with refractory epilepsy and DNET was favored based on the pre-operative imaging, particularly in light of the bright rim sign.
Histology
Sections show a moderately cellular tumor composed of small round tumor cells set within a loose myxoid stroma. Tumor cells contain pale clear cytoplasm, round nuclei and inconspicuous nucleoli. Occasional floating neurons (NeuN positive) are identified. No mitoses, necrosis or microvascular proliferation are seen.
Immunohistochemistry results show tumor cells stain: GFAP: Positive NogoA: Positive IDH1: Positive Topoisomerase proliferation index: 1%
Final diagnosis: dysembryoplastic neuroepithelial tumor (DNET), WHO Grade I.
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