Glioblastoma Multiforme
Findings:
A heterogenously enhancing mass is present in the left
parietal lobe which extends across the splenium of the corpus callosum.
Relative hypointensity is present centrally in the tumor mass on the T2WI,
and there is marked surrounding signal abnormality which extends throughout
most of the left cerebral hemisphere. Additional foci of tumor are present
adjacent to the left frontal horn involving the genu of the corpus callosum.
Differential Diagnosis:
With spread across the corpus callosum, the tumor differential
diagnosis is limited to GBM and lymphoma. Other diagnostic possibilities
include MS and ADEM.
Discussion:
Any T2 signal abnormality in the corpus callosum indicates
tumor and not edema cases of GBM. Likewise, signal abnormality throughout
the cerebral hemisphere in this case reflects microscopic tumor invasion.
The extent of hemispheric signal abnormality raises the possibility that
this was initially a "low grade" infiltrating glioma or gliomatosis which
dedifferentiated due to chromosome deletion (17,9,10 sequence) into a focal
GBM in the parietal lobe.