The patient went on to have a resection.

Histology

The sections show a moderately cellular tumor, forming prominent perivascular pseudorosettes. The tumor cells form cuffs around blood vessels in a fibrillary background. The tumor cells have mildly enlarged round to elongated nuclei and inconspicuous nucleoli. Very occasional mitoses are seen. There is no endothelial cell hyperplasia or necrosis. Spots of microcalcification are present in the background.

Final diagnosis

The features are those of a posterior fossa ependymoma, NOS