Diffuse astrocytoma NOS ("protoplasmic")

Case contributed by Dr Bruno Di Muzio

Presentation

Seizure.

Patient Data

Age: 30 years
Gender: Female
CT

CT Brain

A heterogeneous hypoatteniating mass is identified in the right frontal lobe without contrast enhancement and with areas suggestive of cystic or necrotic component. The lesion seems to be intra-axial. Further investigation with MRI is advised to better characterise such lesion. 

MRI

MRI Brain

A large mass lesion measuring distorts and displaces the middle and inferior frontal gyri on the right. The lesion's epicentre is extra-axial in nature, however, regions of the signal abnormality are also identified within the cortex and the overlying white matter.

Compression of the right lateral ventricle is noted and thinning of the overlying diploic space is present. 

There is no associated contrast enhancement, no raised cerebral blood volume and no evidence of diffusion restriction (in fact ADC values are markedly elevated).  MR spectroscopy at the periphery of the lesion demonstrates decreases in all metabolites.

Review of the preceding CT scan shows that the lesion is predominantly of the low attenuation. No evidence of fat or calcification

Case Discussion

This case was first understood as an extra-axial lesion, however reviewing the images in the multidisciplinary meeting a new conclusion was reached: the tumour involves the cortex in the right frontal lobe and its features are those that suggest a low-grade glioma, such as a protoplasmic type (partial suppression on FLAIR). The adjacent bone remodelling suggests a long-term growth. 

 

The patient underwent surgical resection and the tumour was confirmed histologically. 

Histology

MICROSCOPIC DESCRIPTION: Paraffin sections show a moderately hypercellular astrocytic glioma. Tumour cells are predominantly of protoplasmic morphology with uniform small round hyperchromatic nuclei and a paucity of processes. Prominent microcyst formation is noted in several areas of the tumour. No mitotic figures are identified and there is no vascular endothelial cell proliferation and no necrosis. The features are of diffuse astrocytoma of protoplasmic type (WHO Grade II).

DIAGNOSIS:  Diffuse astrocytoma of protoplasmic type (WHO Grade II).

 

Note: Until recently, protoplasmic astrocytomas were classified as a subtype low-grade astrocytoma, however, in the latest (2016) update to WHO classification of CNS tumours, protoplasmic astrocytomas no longer exists as a distinct entity, but rather are considered as a pattern of certain gliomas, requiring IDH +/- 1p19q status for classification. 

Note: IDH mutation status is not provided in this case and according to the current (2016) WHO classification of CNS tumours, this tumour would, therefore, be designated as a diffuse astrocytoma NOS.

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Case information

rID: 39645
Case created: 14th Sep 2015
Last edited: 22nd Jun 2017
Tag: rmh
Inclusion in quiz mode: Included

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