Presentation
Left facial droop and hemiparesis.
Patient Data
A heterogeneously enhancing mass is present on the right, either peripherally within the right frontal lobe, or extra-axially. It is surrounded by vast quantities of vasogenic pattern edema with local mass effect and minor midline shift.
A solitary vividly enhancing lesion is demonstrated on the right above the sylvian fissure in the inferior frontal gyrus. It is of heterogeneous signal, but predominantly high in T2 signal than adjacent brain, intermediate signal on T1 weighted imaging, and demonstrates a moderate degree of restricted diffusion. Prominent cerebral blood volume (CBV) is present. At the periphery of the lesion and numerous small cystic appearing regions. Beyond this extensive vasogenic type edema extends throughout the frontal and parietal lobes, and tracks into the posterior limb of internal capsule. Unfortunately MR spectroscopy is non-contributory.
The remainder of the brain is unremarkable in appearance.
Conclusion:
Solitary right frontal lesion is difficult to characterize. The three most likely possibilities include an atypical meningioma (e.g. microcystic +/- brain invasion), a peripheral metastasis and a primary glial series tumor.
The patient went on to have a resection.
Histology
MICROSCOPIC DESCRIPTION:
The sections show features of a densely cellular astrocytic tumor. The tumor forms sheets and discrete fascicles. The tumor cells have hyperchromatic and pleomorphic nuclei. Some multinucleated tumor giant cells are noted and some have vacuolated (possibly xanthomatous) cytoplasm. Scattered mitotic figures are identified, up to 5 per 10 high-power fields.
Microvascular proliferation is inconspicuous. Scattered small areas of necrosis are present. Tumor cells extend into the cortex. The background also shows many eosinophilic granular bodies and perivascular lymphocytes. The tumor seems to show pleomorphic xanthoastrocytoma-like morphology including fascicular architecture, eosinophilic granular bodies and perivascular lymphocytes. There are no increased reticulin fibers within the tumor.
The tumor cells are p53 positive. Small numbers are synaptophysin and NeuN positive. The Ki-67 index is about 10%. They are CD34, IDH-1 and MGMT immunostains negative.
FINAL DIAGNOSIS: anaplastic pleomorphic xanthoastrocytoma (WHO Grade III).
Case Discussion
This is an unusual case, and demonstrates the difficulty sometime encountered in even distinguishing intra- vs extra-axial masses.
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