Radiology Quiz 21422 | Radiopaedia.org

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Questions
Findings

True or false: Ependymomas are frequently / usually heterogeneous in signal?

True. Half of ependymomas demonstrate significant signal heterogeneity, which may indicate calcification, necrosis, methemoglobin, hemosiderin, or tumor vascularity.

Question 2

Is this a typical location of an ependymoma in this age group?

Show Answer

Fairly typical. Although they can occur at any age, the posterior fossa tumours tend to present more commonly in the paediatric age group, with a possible second peak around the 3rd decade (as is the case in this patient).

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

Histology

MICROSCOPIC DESCRIPTION: The sections show features of moderately cellular ependymoma.The tumour forms mainly perivascular pseudorosettes. Small numbers of true ependymal rosettes with lumina are also seen. Some of the fragments are lined at the edges by ependymal epithelium. The tumour cells have enlarged round to slightly ovoid nuclei, hyperchromasia and ill-defined eosinophilic cytoplasm. The background is fibrillary. Mitoses are inconspicuous. There is no evidence of endothelial cell hyperplasia or necrosis. The Ki-67 index is 2%.

FINAL DIAGNOSIS: posterior fossa ependymoma (WHO Grade 2).

Note: as molecular profiling was not carried out in this case, it would have the diagnosis of posterior fossa ependymoma not otherwise specified (NOS).