Diffuse astrocytoma NOS

Case contributed by Bruno Di Muzio
Diagnosis certain


Referred from evaluation of a brain lesion found on previous CT scan (not available).

Patient Data

Age: 30 years
Gender: Female

MRI Brain


Ovoid well-defined heterogeneous but predominantly T1 hypointense / T2 hyperintense (which partially suppress on FLAIR) mass involving cortex and white matter of the posteroinferior left parietal lobe. A thin rim of flair hyperintensity surrounds its margin.

No concerning central or marginal enhancement. An equivocal segment of thin rim diffusion restriction at the anterolateral margin. No elevated CBV. No evidence of hemorrhage or calcification. Spectroscopy traces within show elevated choline and depressed NAA, consistent with tumor. Mild local positive mass-effect. Overlying calvarium is unremarkable.

No other intra or extra-axial mass.

Conclusion: Solitary left parietal lobe mass, most likely a low-grade glioma.


MICROSCOPIC DESCRIPTION:  The sections show features of a moderately cellular astrocytic tumor. The tumor cells are of mixed fibrillary and protoplasmic types. Small numbers of gemistocytes are also seen. The tumor cells have enlarged hyperchromatic nuclei and variable amounts of cytoplasm. Focal microcystic change is seen in the background. Mitoses are inconspicuous. No endothelial cell hyperplasia or necrosis is present. Tumor cells are seen in the cortex. There is no oligodendroglial component. The features are those of diffuse astrocytoma. The Ki-67 index is 3-4%. IDH-1 immunostain is negative.

FINAL DIAGNOSIS: Diffuse astrocytoma (WHO Grade II).

Case Discussion

Note: IDH mutation status is not provided in this case and according to the (2021) WHO classification of CNS tumors, this tumor would, therefore, be designated as a diffuse astrocytoma NOS.

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