Oligoastrocytoma NOS

Case contributed by Assoc Prof Frank Gaillard

CT Brain

Calcified mass in the right occipital lobe. 


MRI Brain

Heterogeneously calcified mass in the mesial occipital lobe on the right with enhancing an cystic components. 



The sections show a densely calcified, moderately hypercellular glial tumor composed of oligodendroglial and fibrillary astrocytic cells arranged in diffuse sheets. Both components show mild nuclear pleomorphism. No mitotic figures are seen and there is no vascular endothelial cell proliferation and no necrosis. The Ki-67/MIB-1 proliferation index is approximately 3%. The features are of oligoastrocytoma.

Case Discussion

This case was histologically proven as an oligoastrocytoma (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. 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. Given extensive calcification, this is likely to be 1p19q co-deleted and most likely would be classified as an oligodendroglioma. Unfortunately, it is not possible to establish this in this historical case, as such one must fall back on the original histological diagnosis. 


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Case information

rID: 4336
Published: 10th Aug 2008
Last edited: 2nd Jan 2020
Inclusion in quiz mode: Included