Cellular tumor composed of proliferating monomorphic elongated cells arranged around markedly thickened and extensively hyalinized blood vessels with their nuclei being placed away from the basement membrane of these vessels (ependymal pseudorosettes). In areas, these cells are confluent forming sheet-like masses. In other smaller foci, these cells form pseudorosettes around fibrillary processes. Foci of tumor necrosis are noted. Areas of calcification are observed. Despite marked increase in cellularity, mitotic activity is not increased and cellular features do not show anaplastic features enough to qualify for anaplastic astrocytoma. This is consistent with ependymoma, WHO grade 2.
Posterior fossa mass (cystic with solid nodule).
Soft tissue fragments collectively measured 4.5x3.5x1 cm, largest measured 2.5x2x1 cm.
Posterior Fossa mass, Biopsy: