Medullobastoma

Case contributed by A.Prof Frank Gaillard

Presentation

Ataxia.

Patient Data

Age: 25 years
Gender: Male
Modality: MRI

A rounded mass is centred on the vermis of the cerebellum, demonstrating only mild enhancement but prominent restricted diffusion, implying high cellularity. 

In this location, the diagnosis most likely represents a medulloblastoma

Case Discussion

The patient went on to have surgery. 

Histology

MICROSCOPIC DESCRIPTION: Paraffin sections show fragments of a densely hypercellular tumour. This is composed of cells with small round hyperchromatic nuclei with delicate processes, arranged in diffuse sheets. A vague nodularity is noted in some areas. Moderate numbers of mitotic and apoptotic figures are noted. There is no microvascular proliferation and no necrosis is seen.

Immunohistochemistry shows strong nuclear staining in tumour cells for INI-1 and strong cytoplasmic staining for beta-catenin and CD56. There is patchy weak staining for synaptophysin and nestin. No staining for CD3, CD20, GFAP, TTF-1, pancytokeratin AE1/AE3, cytokeratin CAM5.2 or epithelial membrane antigen (EMA) is seen in tumour cells.

p53 appears to be wild type.

FINAL DIAGNOSIS: Medulloblastoma (WHO Grade IV).

Unfortunately, immunohistochemistry to determine molecular sub-type is unavailable. 

Disucssion

Although we think of medulloblastomas as being paediatric tumours, they are not uncommonly found in young adults. Then, they are typically located in the hemisphere and are of SHH subtype. They can, however, also occur in the vermis. 

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Case Information

rID: 44525
Case created: 26th Apr 2016
Last edited: 24th Nov 2016
Inclusion in quiz mode: Included

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