Typical appearances of a butterfly glioma. The patient went on to have a biopsy. 

Histology

MICROSCOPIC DESCRIPTION: Paraffin sections show fragments of a densely hypercellular glial tumor.  Tumor cells are a mixture of fibrillary and gemistocytic astrocytes and several markedly pleomorphic multinucleated tumor giant cells are also noted.  Scattered mitotic figures are identified. There are foci of necrosis as well as microvascular proliferation with endothelial cell hyperplasia.  

FINAL 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.