Oligoastrocytoma NOS

Case contributed by Assoc Prof Frank Gaillard



Patient Data

Age: 25 years
Gender: Female

A relatively well circumscribed intra-axial region of low attenuation involves the frontal operculum and insular cortex and temporal pole. There is no appreciable enhancement. 


There is a region of high FLAIR signal centered on the right insula, extending into the right inferior and posterior frontal lobe and anterosuperior temporal lobe. No contrast enhancement. There is increased perfusion, particularly in the right frontal white matter, corresponding to patchy areas of diffusion restriction.

No evidence of blood products. Spectroscopy in an area of high FLAIR signal shows an increased creatine: choline ratio, and slightly reduced NAA. Mild mass effect on the right lateral ventricle with no midline shift. No futher lesion.


Right frontal tumor has features of a glioma with increased perfusion either indicates an oligodendroglial component or an anaplastic (WHO III) diffuse astrocytoma.


Case Discussion

The patient went on to have a craniotomy and biopsy. 


The sections show features of a moderately cellular glial tumor. There is a proliferation of predominantly neoplastic astrocytes. They are of mostly fibrillary type with smaller amounts of protoplasmic astrocytes. The former cells have elongated, angulated and hyperchromatic nuclei and much rounder nuclei in the latter cells.

A minor population of neoplastic oligodendroglial cells is also present (less than 10%). These cells have round nuclei and perinuclear haloes. They extend into the cortex with secondary structuring. Scattered mitoses are seen but there are less than 5 per 10 high-power fields. No microvascular proliferation or necrosis is present. The features are those of oligoastrocytoma. The tumor cells are IDH-1 positive. The Ki-67 index is about 10%. They are p53 and MGMT negative. The neoplastic astrocytes are ATRX negative.


Oligoastrocytoma (NOS) NOS (WHO Grade II).

NOTE: This case predates the 2016 WHO classification of CNS tumor 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 recognized in the current classification for cases where molecular information is unavailable. 

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Case information

rID: 34581
Published: 7th May 2015
Last edited: 14th Aug 2019
Inclusion in quiz mode: Included

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