Posterior fossa ependymoma

Case contributed by Assoc Prof Frank Gaillard

Presentation

Headache.

Patient Data

Age: 20 years
Gender: Female
mri

Extra-axial right cerebllopontine angle mass with the PICA running though it invaginates out of/into the lateral foramen of Luschka. It demonstrates modest heterogeneous enhancement and facilitated diffusion. 

Conclusion

Ependymoma is by far the most likely diagnosis.  An exophytic brainstem glioma is unlikely (e.g. pilomyxoid astrocytomas). It is definitely not an epidermoid cyst nor an unusual medulloblastoma.

pathology

The patient went on to have a resection and made an unremarkable recovery. 

Histology

There are portions of a hypercellular glial neoplasm showing perivascular pseudo-rosetting with anucleated zones of fibrillary matrix. The neoplastic cells have round to elongated relatively small nuclei with salt and pepper chromatin pattern. Focal geographic necrosis is present but features of anaplasia are not identified. There is no endothelial proliferation, no palisaded necrosis and no brisk mitotic activity. Immunohistochemistry shows positive labeling of the anucleated perivascular fibrillary zones for GFAP. Occasional peri-nuclear labeling is noted for EMA.

FINAL DIAGNOSIS: posterior fossa ependymoma (WHO grade2).

Case Discussion

Most posterior fossa ependymomas enhance more vividly than this case, but the soft plastic appearance of this tumor, the demographics and the alternative diagnosis made a preoperative diagnosis possible. 

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