The patient went on to have surgery.

Histology

MICROSCOPIC DESCRIPTION: Sections show a moderately cellular tumor with a fibrillary background forming prominent perivascular pseudorosettes. True rosettes are absent. Tumor cells demonstrate mildly enlarged elongated nuclei and inconspicuous nucleoli. No mitoses are seen. No microvascular proliferation or necrosis is seen.

Immunohistochemically tumor cells stain: GFAP+ and EMA+ (perinuclear dot positivity). The Topoisomerase proliferation index is approximately: 1-2%. .

FINAL DIAGNOSIS: Ependymoma (WHO Grade II).