Anaplastic oligodendroglioma NOS
The patient went on to have surgery.
This is a high-grade mixed oligoastrocytoma that shows necrosis; which should be classified as glioblastoma with oligodendroglial component, although it might have a better prognosis than standard glioblastoma.
The previous material was reviewed and it shows low-grade oligodendroglioma.
GFAP+, P53+ strongly, KI-67 high (over 25%)
Final diagnosis: Glioblastoma with oligodendroglial component, WHO grade IV.
Note: Under the current (2016) WHO classification of CNS tumors, this tumor is not easily classified. If the original tumor was indeed an oligodendroglioma (IDH mutant, 1p19q co-deleted) then this is now an anaplastic oligodendroglioma and not a glioblastoma.