Medulloblastoma

Case contributed by A.Prof Frank Gaillard

Presentation

Ataxia, gait disturbance and vertigo for a few weeks.

Patient Data

Age: 35 years
Gender: Female

CT brain

Modality: CT

A single sagittal image from a CT of the brain demonstrates a heterogeneous slightly hyperdense mass above the bulk of the cerebellum and posterior to the midbrain. Pineal calcifications are displaced superiorly and the mass is clearly below the internal cerebral veins / vein of Galen. 

MRI brain

Modality: MRI

An aggressive appearing tumour is seen on the pineal region / tectal plate / superior vermis. It measures 37 x 40 x 40 mm, is of slight increased signal intensity on T2 weighted images, with multiple areas of cystic change, and hypointense on T1, with strikingly restricted diffusion, and moderate enhancement of the non cystic components. It fills the tentorial incisura, displaces the tectal plate to the right and anteriorly, extends into the perimesencephalic cistern on the left, and into the medial aspect of the left occipital lobe towards the ependyma of the lateral ventricle. The tumour and displaced superior vermis of the cerebellum cannot be differentiated, indicating either invasion or origin from the cerebellum.

The internal cerebral veins are clearly seen immediately above the main tumour mass as is the pineal galnd. The vein of Galen and straight sinus elevated immediately above the mass appear patent.

There is mild hydrocephalus secondary to aqueduct compression with minimal transependymal oedema. Cerebral parenchymal signal intensity and architecture elsewhere normal. This no evidence of CSF spread of tumour in intracranial compartment beyond the main tumour mass.

Annotated images

Modality: Annotated image

The mass ( * ) is located below the vein of Galen (blue arrows) and displaces the pineal gland and calcifications (yellow arrows)  anterosuperiorly. 

Histology

Modality: Pathology

The patient went on to have a craniotomy and resection of the tumour. 

Histology

The sections show a densely cellular malignant tumour, forming mainly diffuse sheets. Scattered interspersed pale islands and nests of cells are present. Within these islands, the tumour has more linear and cord-like arrangement. The stroma is somewhat more fibrillary. Occasional poorly formed rosettes are identified elsewhere.  The tumour cells have high N/C ratio with enlarged round nuclei, small nucleoli, granular chromatin and scanty cytoplasm. No mature neurons are present.  Sparse mitoses are seen (0-1 mitosis per 10 high power fields).  There are scattered apoptotic bodies throughout the tumour. No endothelial cell hyperplasia is identified.  The background is rich in reticulin fibres, apart from the pale islands. The tumour cells are synaptophysin and B-tubulin positive. There is focal GFAP positivity. The Ki-67 index is about 15%. Neurofilament, chromogranin and CAM5.2
are negative.

The presence of reticulin-poor pale islands has only be described in medulloblastoma and not in pineal parenchymal tumour.

FINAL DIAGNOSIS:

Posterior fossa tumour: Desmoplastic / nodular medulloblastoma (WHO Grade IV).

Case Discussion

This case illustrates a somewhat atypical location for a medulloblastoma, which raised the preoperative possibility of a pineal region tumour, although the pineal gland seemed to be displaced superiorly. 

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Case Information

rID: 15445
Case created: 17th Oct 2011
Last edited: 7th Nov 2015
Inclusion in quiz mode: Included

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