Pilocytic astrocytoma of the third ventricle

Case contributed by A.Prof Frank Gaillard

Presentation

Headache.

Patient Data

Age: 24
Gender: Male
Modality: CT

An irregularly enhancing mass centered below the foramina of Munro. No calcification. 

Modality: MRI

Large intraaxial mass lesion, measuring 3.5 x 2.5 x 2.5cm in perpendicular dimensions, it appears to be within the 3rd ventricle, obstructing the monro foramina bilaterally, causing severe bilateral obstructive hydrocephalus with transependymal oedema evident. The mass inferiorly displaces the floor of the third ventricle floor, hypothalamus and mammillary bodies and optic chiasm. 

Irregular enhancement. There is no significant surrounding edema, with no significant diffusion restriction (>1200 x 10-6 mm2/s). Decreased NAA, increased Choline and CBV noted within the mass.

Right frontal ventricular drain in situ, traversing the left lateral ventricle with the tip appears within the left thalamus.

Histology

Modality: Pathology

The patient went on to have an endoscopic biopsy. 

Histology

MICROSCOPIC DESCRIPTION:

The sections show features of a moderately cellular glial tumour. Scattered bipolar astrocytes are seen, which show focal somewhat fascicular arrangement. The tumour cells have elongated and hyperchromatic nuclei. No Rosenthal fibres or eosinophilic granular bodies are seen in the background. No mitoses are present. No microvascular proliferation or necrosis is identified. The features are those of pilocytic astrocytoma. The topoisomerase index is less than 1%. IDH-1 immunostain is negative.

DIAGNOSIS: Hypothalamic tumour: Pilocytic astrocytoma (WHO Grade I).

Histology courtesy of Dr Alpha Tsui, Royal Melbourne Hospital. 

Case Discussion

Appreciating that this mass is essentially within the third ventricle without surrounding oedema or restricted diffusion helps point you towards a low grade tumour. In this age group a pilocytic astrocytoma should be favoured. 

 

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Case Information

rID: 34797
Case created: 8th Mar 2015
Last edited: 28th Sep 2015
Inclusion in quiz mode: Included

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