Ganglioglioma (cerebral)

There is an intra-axial mass lesion involving the right posterior frontal lobe just superior to the Sylvian fissure.

The lesion has a more discrete cortical and sub-cortical component that measures 29mm x 24mm, demonstrating faint enhancement, however, more extensive T2 and FLAIR high signal is noted involving the right frontal opercular lobe, right insula region, right frontal corona radiata, right internal capsule (posterior limb) and body of the corpus callosum.

The abnormal signal within the corona radiata demonstrates restricted diffusion. There is subsequently 9.6 mm left-sided midline shift with effacement of the right lateral ventricle.

No definite imaging abnormality of the ocular globes currently demonstrated.

Conclusion:

There is a mass lesion involving the right frontal lobe with a more discrete cortical and sub-cortical component above the Sylvian fissure and a more infiltrative component extending to the right frontal corona radiata and corpus callosum - as detailed above.The imaging findings are not consistent with an abscess.

Likely differentials to consider include an intermediate grade glial series tumor and lymphoma (in view of the restricted diffusion involving the corona radiata).

MICROSCOPIC DESCRIPTION:

The sections show a variably cellular tumor composed of a mixture of oligodendroglial and astrocytic cells and with intermingled enlarged and atypical ganglion cells. Scattered bi-nucleate ganglion cells are identified. The oligodendroglial and astrocytic tumor cells show mild nuclear pleomorphism. Scattered thick-walled blood vesels are identified but there is no evidence of endothelial cell hyperplasia. No mitotic figures are identified and there is no necrosis.

IMMUNOHISTOCHEMISTRY:

• GFAP positive in astrocytic cells
• NeuN positive in neuronal cells
• Nogo A positive in oligodendroglial cells
• IDH-1 R132H mutated
• MGMT negative
• p53 positive in astrocytic cells
• p16 positive
• Synaptophysin positive in neuronal cells
• Topoisomerase labeling index: Approximately 3%.
• BRAF V600E is negative

DIAGNOSIS: Ganglioglioma (WHO Grade I)

The glial component of this ganglioglioma is a mixture of oligodendroglial and astrocytic components and is IDH-1 R132H mutated.