Protoplasmic astrocytoma

Case contributed by Dr Bruno Di Muzio

Presentation

Seizure.

Patient Data

Age: 31
Gender: Female

CT Brain

Modality: CT

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 Brain

Modality: MRI

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.

Thinning of the overlying diploic space is noted.

There is no associated contrast enhancement.

No raised cerebral blood volume.

No evidence of diffusion restriction.

The ADC is 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

Conclusion: A large mass lesion predominantly extra-axial overlies the right frontal lobe. A definitive diagnosis is not reached. The heterogeneity of signal intensity as against arachnoid cyst. The elevated ADC is unusual for epidermoid. A neuroglial cyst is thought a more likely diagnosis. A primary intra-axial tumour is thought unlikely

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 remodeling suggest a long-term growing. 

 

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

MICROSCOPIC DESCRIPTION: 1-4: 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: 1-4: Brain tumour: Diffuse astrocytoma of protoplasmic type (WHO Grade II).

 

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. 

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Case Information

rID: 39645
Case created: 14th Sep 2015
Last edited: 21st Jul 2016
Tag: rmh
Inclusion in quiz mode: Included

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