The patient went on to have surgery. 

Histology

MICROSCOPIC DESCRIPTION: Sections show fragments of a moderately hypercellular astrocytic glioma. Tumor cells show marked nuclear and cellular pleomorphism. Focally tumor cells demonstrate gemistocytic morphology. Frequent mitotic figures are identified. There is prominent microvascular proliferation and areas of palisaded tumor necrosis present. 

DIAGNOSIS: Glioblastoma (WHO Grade IV).

Note: IDH mutation status is not provided in this case and according to the current (2016) WHO classification of CNS tumors, this tumor would, therefore, be designated as a glioblastoma NOS. 

Discussion

Gliomas that involve the midline structures (i.e. corpus callosum) and extend into the cerebral hemispheres are colloquially given the name "butterfly glioma", being somewhat reminiscent of the shape of a butterfly.