Primary CNS lymphoma
Altered mental state.
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Multiple periventricular and juxtacortical regions of globular T2 signal hyperintensity are identified in the right and left frontal lobes, and left paramedian parietal lobe, with smaller region of abnormality in a subcortical location in the left posterolateral temporal lobe and another lesion centered on the right middle cerebellar peduncle. The periventricular lesions involve the anterior aspect of the corpus callosum body. Lesions are almost entirely T2 hypointense, although 2 of the right frontal periventricular lesions contain small central focus of hyperintensity. Supratentorial lesions demonstrate solid rather than peripheral or 'leading-edge' enhancement, while the right cerebellar peduncle lesion has blotchy peripheral enhancement. There is no low ADC diffusion restriction associated with the lesions. No subependymal or leptomeningeal enhancement is identified. No hydrocephalus. MR angiogram demonstrates no intracranial stenosis or occlusion. There is no vessel wall irregularity.
Conclusion: The morphology of these globular periventricular, subcortical and cerebellar peduncle T2 hyperintense lesions raises the possibility primary CNS lymphoma. Demyelination (acute disseminated encephalomyelitis) is also a consideration although open-ring peripheral enhancement is usually seen.
The patient went on to have a biopsy.
MICROSCOPIC DESCRIPTION: The sections show cerebral cortex and white matter. There is a prominent band-like infiltrate of atypical large mononuclear cells within the sub-pial molecular layer and a relatively even distribution of similar cells throughout the cerebral cortex with patchy perivascular aggregation. Lesser numbers of the atypical cells are present in white matter. The atypical cells have round, oval and angulated nuclei with an open arrangement of chromatin, conspicuous nucleoli and a variable amount of pale cytoplasm. Frequent mitotic figures are noted. There is a background population of reactive astrocytes.
Immunohistochemistry shows the atypical large cells to be CD20+, bcl-6+, bcl-2+, MUM-1+, CD10-, CD23-, cyclin D1-, CD5-, CD30-, CD68-, CD1a-. Moderate numbers of small CD3+ T lymphocytes are admixed with the large atypical cells. No staining for SV-40/BKV is seen.
In situ hybridization for Epstein-Barr virus (EBER-CISH) is NEGATIVE
FINAL DIAGNOSIS: non-Hodgkin's large B-cell CNS lymphoma (non-germinal center phenotype).