Radiology Quiz 13715 | Radiopaedia.org

Images
Questions
Findings

Is this the typical location for a medulloblastoma?

Yes for children, but in adults they are more frequently located in unusual locations. In such cases the tumour is also more likely to be poorly marginated and demonstrate larger cyst formation. Adult medulloblastomas are usually located laterally in the cerebellar hemispheres, with only 28% centred in the vermis.

Question 2

What is the prognosis for this patient?

Show Answer

Presence of CSF metastases results in a 5-year survival of only ~ 20%.

The patient went on to have a craniotomy and excision of the posterior fossa mass.

Histology

MICROSCOPIC DESCRIPTION: Paraffin sections show a densely hypercellular tumour involving cerebellum with features of medullablastoma. Tumour cells have small irregularly shaped hyperchromatic nuclei and form well developed Homer Wright type rosettes. In addition there is a diffuse sheeted arrangement and a desmoplastic pattern is noted focally. Some pale areas are also seen. There are frequent mitotic figures and prominent apoptotic activity. A focus of confluent necrosis with dystrophic calcification is also noted. Tumour predominantly involves cerebellar white matter but focally is seen to stream through cerebellar cortex from a persistent external granular layer. Tumour also extends to overlying leptomeninges.

Immunohistochemistry shows strong diffuse staining for synaptophysin in tumour cells and focal weak staining for GFAP. This profile is in keeping with medulloblastoma. The topoisomerase labelling index is aprroximately 30%.

FINAL DIAGNOSIS: Medulloblastoma (WHO grade IV).