Anaplastic ependymoma, light micrograph. Classic ependymoma is a爓ell-circumscribed and a cellular neoplasm爓ith sheet-like growth pattern. The tumour cells are frequently arranged around blood vessels creating爌erivascular pseudorosettes. Vast majority of ependymomas are爄nfratentorial燼nd爄nvolve the 4th ventricle, mostly in children. The diagnosis of anaplastic ependymoma (WHO Grade III) requires hypercellularity, cytologic atypia, increased mitotic activity, and microvascular proliferation as shown in this image.