Oligoastrocytoma NOS

Case contributed by Dr Bruno Di Muzio

Presentation

Not available.

Patient Data

Age: 30 years
Gender: Male
CT

CT brain shows a right frontal hypodense subcortical area that does not enhance after contrast administration. No acute intracranial haemorrhage. Cortical volume is age-appropriate. No hydrocephalus. The basal cisterns are unremarkable. The paranasal sinuses and mastoid air cells are clear. No suspicious osseous lesion.

MRI

MRI brain shows a right precentral frontal superior gyrus lesion characterised by two small subcortical T2 hyperintense foci surrounded by FLAIR hyperintensities and without contrast enhancement. The remaining brain parenchyma is unremarkable. 

MRI

MRI brain demonstrates again the precentral lesion slightly increased compared to the previous MRI exam and now showing linear enhancement in its borders. The remaining brain parenchyma is unremarkable. 

MICROSCOPIC DESCRIPTION: Sections show white matter invaded by a diffuse population of atypical glial cells with enlarged, round nuclei many of which are surrounded by clear haloes. There is a network of fine capillaries in the background and some small calcified foci. Scattered mitotic figures are identified (2/10HPF). No endothelial cell hyperplasia or necrosis is seen.

IMMUNOHISTOCHEMISTRY:

  • GFAP positive
  • Nogo A positive
  • IDH-1 positive
  • MGMT negative (likely methylated)
  • p53 positive in a small number of tumour cells
  • Topoisomerase labelling index: Approximately 10%. 

DIAGNOSIS: Right precentral gyrus lesion: Oligoastrocytoma (NOS) (WHO Grade II)

Case Discussion

Both CT and MRI illustrate features of a low-grade glioma tumour in the right precentral frontal lobe.

Oligoastrocytomas are infiltrating gliomas composed of a mixture of two distinct neoplastic cell types resembling the tumour cells in oligodendroglioma and astrocytoma. They are a WHO grade II tumours and preferentially develop in adults between 35-45 years of age. 

NOTE: This case predates the 2016 WHO classification of CNS tumour revision. As no 1p19q co-deletion status is available a formal diagnosis cannot be reached and the NOS is therefore used (not otherwise specified) - which is recognised in the current classification for cases where molecular information is unavailable. It should also be noted, that under the new classification both an astrocytic and oligodendroglial component needs to be identified, each with its own molecular markers. True oligoastrocytomas are therefore going to be rare, and this case would most likely be classified as either an astrocytoma or an oligodendroglioma. 

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Case information

rID: 34944
Case created: 16th Mar 2015
Last edited: 21st Dec 2016
Tag: rmh
Inclusion in quiz mode: Included

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