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Pre and contrast scans were performed including an intracranial MRA. Right distal ICA aneurysm once again noted, dimensions 10.5 x 9.5 x 10.1 mm.
There is a focal lesion in the anteromedial aspect of the left occipitotemporal region.The lesion is peripherally located and appears to involve cortex and subcortical white matter. A rounded T2 hyperintense component measures 11.3 x 10 .8 mm in axial dimensions and enhances post administration of contrast. There is a small 3 mm nodule anterior to this. Small amount of surrounding vasogenic edema. No susceptibility artifact or restricted diffusion.
The left medial occipitotemporal lesion is favored to represent a low grade neoplastic lesion, differential diagnoses include DNET, ganglioglioma and low grade glial tumor (pilocytic astrocytoma, PXA).
The patient went on to have a resection.
Paraffin sections show a mild to moderately hypercellular tumor with some normal cortex included in the biopsy. The tumor comprises haphazardly arranged atypical astrocytes with mildly pleomorphic and hyperchromatic nuclei. Many astrocytes show bipolar cytoplasmic processes. There is a background of loose myxoid stroma. Scattered neurons are seen within the tumor. They show mild architectural disarray and loss of orientation. Small numbers of scattered lymphocytes are seen dispersed within the tumor as well as cuffing some of the capillaries. Few eosinophilic granular bodies are identfied. There are no rosenthal fibers. No mitotic figures are identified. There is no endothelial cell hyperplasia or necrosis.
The astrocytic component shows strong and diffuse staining for GFAP. The ganglion cells are highlighted with Neu-N. There is no staining by the tumor cells for IDH-1. The Ki-67 proliferative index is 2-3%. The features are those of a low grade glioneuronal tumor with features favoring a ganglioglioma.
It is difficult to accurately grade this tumor. However, the astrocytic component is dominant and has features of WHO Grade II astrocytoma.
Left occipital lesion: Low grade glioneuronal tumor with features favoring ganglioglioma.