Presentation
Recent onset of increasing headaches, worse in the morning. Abnormal CT (not available). Further assessment with MRI.
Patient Data
Pre and post contrast scans were performed. There is a lesion with lobulated margins filling the inferior aspect of the fourth ventricle, extending into the foramen of Magendie. Lesion has a focal cystic areas within it and demonstrates heterogeneous enhancement, with non enhancement of the focal cystic areas of large areas of solid enhancement. Moderate restriced diffusion, similar to the adjacent cerebellar hemisphere (on ADC) with a component of T2 shine through. The lesion measures 17 x 31 x 29 mm. There is obstructive hydrocephalus and effacement of the cortical sulci. No further abnormal enhancement is identified.
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 tumor 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 tumor 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).
Case Discussion
This case demonstrates fairly typical appearances of a posterior fossa ependymoma.