Presentation
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Patient Data
There is a mass centered in the posterior body and splenium of the corpus callosum extending towards the right in what appears to represent a subependymal distribution. It has a hyperdense soft tissue component and a likely central hypodense/necrotic area. Significant surrounding vasogenic edema involving both hemispheres, but more prominent on the right. There is the distortion of the posterior horn of the right lateral ventricle, the calcification adjacent to the mass represents the physiological choroid plexus calcification.
The mass confirms to have intense homogeneous enhancement. Although some flecks of microhemorrhage are present, there is a clear rim of restricted diffusion in its solid marginal components that are not hemorrhagic related.
Macroscopy:
A. Labeled "Splenium of CC via right keene's point". Four pale tan tissues 4 mm to 7 mm. Part submitted as smears and part for frozen.
B. Labeled "Splenium of corpus callosum enhancing lesion". Pale tan soft tissue 5mm. Smears prepared.
C. Labeled "Right Keene's point approach to splenium". Multiple pale tan soft tissue 4 mm to 7 mm.
Microscopy:
A. Formalin fixed, paraffin embedded sections show cerebral cortical tissue exhibiting changes of reactive gliosis and focal infiltration by a population of large malignant cells of lymphoid appearance.
B. Cytological smears performed intraoperatively show a population of large atypical single cells of lymphoid appearance within a background of necrotic debris. Tissue was not submitted for histological examination.
C. Formalin fixed, paraffin embedded sections show tissue fragments within which there is perivascular clustering by a population of large atypical cells of lymphoid appearance. There are surrounding changes of reactive gliosis.
Tumor cells immunoreact with antibodies against CD20, MUM-1 and Bcl-2 and show patchy immunoreactivity with antibodies against Bcl-6 and c-myc (> 40%). CD10 immunohistochemistry is negative. Ki67 proliferative index exceeds 80%.
In situ hybridization for EBV (EBER) is negative.
Diagnostic Opinion: Splenium of corpus callosum, biopsies: Diffuse large B-cell lymphoma.
Case Discussion
This case illustrates imaging features of a callosal periventricular lesion in an elderly patient, which differential is made basically in between GBM and lymphoma (primary central nervous system lymphoma). Note that the area with microhemorrhage and the rim appearances and not that striking, although clearly present, low ADC areas can make it difficult to distinguish both possible etiologies, but the pattern of enhancement, which is vivid and has some fuzzy margins, is quite suggestive for lymphoma; further confirmed on biopsy.
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