The patient went on to have a craniotomy and resection of the mass. 

Histology

Sections show a low-grade glial tumor with areas of calcification and microcyst formation. The cysts contain colloid-like material. The tumor cells are relatively small in size, with round to oval nuclei, and are arranged in small linear clusters and around vessels, rendering a perivascular pseudorosette pattern. A few areas display a modest increase in cellularity. For the most part, cellularity is relatively low. Mitotic activity is not conspicuous.

Final Diagnosis: subependymoma