Oligodendroglioma NOS (grade 3)

The patient now went on to have surgery. 

Histology

This is a high-grade mixed oligoastrocytoma that shows necrosis; which should beat the time of this case was 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.

Immunohistochemistry: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 tumours, this tumour is not easily classified. If the original tumour was indeed an oligodendroglioma (IDH mutant, 1p19q co-deleted) then this is now an anaplastic oligodendroglioma and not a glioblastoma.

As molecular status is unavailable this is best thought of as an oligodendroglioma NOS progressing to an anaplastic oligodendroglioma NOS grade 3.

Right frontal mass, largely involving cortex with high T2 signal and no T2/FLAIR mismatch exerts significant local mass effect. No calcification or haemorrhage or solid enhancement or necrosis.

Path proven oligodendroglioma, WHO grade II.

Note: IDH mutation and 1p19q co-deletion status are not provided, are now required for the diagnosis of oligodendroglioma, although this does seem likely given the age and morphology. It should therefore be denoted as oligodendroglioma not otherwise specified (NOS). 

Followup

The patient was on regular MRI brain follow-up after surgical resection and radiotherapy. Subsequent follow-up revealsrevealed the development of a small enhancing nodule in the surgical bed (not shown), so recurrence was suspected. PET brain confirmed the presence of high metabolic rate lesion correlating to the MRI finding.

However, the patient refused to undergo another surgical resection.