Presentation
Left sided facial droop.
Patient Data
There is a nodular hypoattenuating area involving the right thalamus and demonstrating uncertain local mass-effect. The features are non-specific and with a broad differential diagnosis, which includes glial series tumor, infarction, and infection. Further assessment with MRI is recommended.
Previously demonstrated hypodense focus centered within the right thalamus abutting the third ventricle corresponds to slightly ill-defined ovoid T2/ FLAIR hyperintense mass with wispy central and peripheral enhancement. There is mild diffusion restriction, however, no convincing elevation in CBV. Spectroscopy demonstrates normal spectral traces (one trace with elevated Choline has been performed over the right lateral and 3rd ventricle which is likely artefactual). Associated mild mass effect on the third ventricle, however, no hydrocephalus. No other space occupying lesion or abnormal enhancement. There is multiple subcortical and deep white matter FLAIR hyperintense foci which are more than expected for patient age, however, nonspecific in nature.
MICROSCOPIC DESCRIPTION: 1-3. Sections show white matter mostly replaced by diffuse sheets of CD68+/CD1a-/S100- foamy macrophages containing intracytoplasmic granular material (Luxsol Fast Blue positive, consistent with myelin). The Neurofilament stain demonstrates associated axonal loss. There are small perivascular cuffs of CD3+ T-cells present (CD8>CD4). No vasculitis is seen. The GFAP stain highlights reactive astrocytes. The SV40/BK immunostain is negative for JC virus. No viral inclusions or granulomas are seen. The IDH-1 stain is negative. There is no evidence of tumor.
DIAGNOSIS: 1-3. Brain, right thalamic lesion: Features favoring inflammatory demyelination; no tumor seen.
Case Discussion
Tumefactive demyelinating lesion, also sometimes referred to as monofocal acute inflammatory demyelination, is a locally aggressive form of demyelination, usually manifesting as a solitary lesion greater than 2 cm that, as in this case, may mimic a neoplasm on imaging.