Inflammatory demyelination

The mass, which extends around the ventricle, demonstrates heterogeneous areas of enhancement, within which there is a central non enhancement suggestive of necrosis. There is minimal elevation of cerebral blood volume in the bulk of the enhancing component anteriorly. MR spectroscopy demonstrates significant elevation of choline, depression of NAA, and elevation of lactate (not shown). ADC values are facilitated. There is considerable surrounding edema. The remainder of the brain is unremarkable in appearance.

Biopsy tract through frontal lobe noted. Left lateral ventricle posterior to the mass (trigone and temporal horn) is dilated due to impairment of outflow through foramen of Munro which is compressed by the aforementioned mass. The right lateral ventricle, the third ventricle and fourth ventricles are unremarkable. 

MRI of the cervical spine (not shown) is normal. 

Conclusion: Left frontal lobe mass may represent a high grade glioma but is a little unusual in appearance given the absence of restricted diffusion or elevated CBV. 

The patient went on to have a second biopsy.

MICROSCOPIC DESCRIPTION:

The sections show scattered astrocytes, some histiocytes and microglial cells in the white matter. The astrocytes appear reactive, showing gemistocytic form and radiating processes. Occasional perivascular CD3+ T-lymphocytes are noted. The astrocytes are IDH-1 immunostain negative. ATRX shows no loss of staining. The topoisomerase index is less than 1%.

The prior biopsy has also been reviewed. It contains a larger amount of tissue, showing scattered foamy macrophages, along with reactive gliosis and perivascular lymphocytes. The appearances are consistent with inflammatory demyelination. No tumor is seen.

FINAL DIAGNOSIS: Inflammatory demyelination.