The patient went on to have a resection. 

Histology

Paraffin sections show fragments of a moderately hypercellular tumor composed of cells with uniform round and oval nuclei with finely granular chromatin and delicate processes. These are arranged in diffuse sheets and perivascular pseudo-rosettes. No mitotic figures are seen and there is no vascular endothelial cell hyperplasia and no necrosis. Myxoid-mucinous material is noted in some of the pseudo-rosettes interposed between the central blood vessel and the surrounding corona of tumor cells.

Tumor cells show strong immunostaining for GFAP. Weak staining for epithelial membrane antigen (EMA) is noted in some pseudo-rosettes. The Ki-67/MIB-1 labeling index is <1%.

FINAL DIAGNOSIS: myxopapillary ependymoma (WHO Grade I)