Primary CNS lymphoma
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A mass in the region of the right basal nuclei is vividly enhancing, with a small central non-enhancing component that is mildly hyperintense on T2 FLAIR and hypointense on T1. There is extensive T2 FLAIR signal abnormality surrounding the right basal nuclei lesion. The mass demonstrates mildly increased rCBV. MR spectroscopy through this region demonstrates elevated lipid/lactate of the enhancing regions, with increased choline and moderately reduced NAA. The enhancing component of the lesion demonstrates striking restricted diffusion (ADC 450-500 x 10^- 6 mm^2/s) indicating high cellularity.
Diffusion restriction is also present in the caudate head suggesting an infarct.
Given the very low ADC values of the solid component, a very highly cellular tumor is suspected, with lymphoma being most likely. A differential worth considering but thought much less likely is glioblastoma. Toxoplasmosis would not be expected to have this degree of mass like enhancement or low ADC in the enhancing component.
The patient went on to have a biopsy.
Sections of brain tissue show a densely cellular, diffuse proliferation of medium-to-large sized malignant lymphoid cells containing scant cytoplasm, high N:C ratio and hyperchromatic oval nuclei with prominent nucleoli.
Immunohistochemical results show tumor cells stain: POSITIVE: Co20, CD79a, BCLZ, BCL6, MUMl, CMYC 50%, IG67 80% NEGATIVE: CD3, Co10, EBER-CISH
FINAL DIAGNOSIS: diffuse large B-cell cerebral lymphoma, activated B-cell (ABC) phenotype.