Tumors with Ependymal-Like Features

Rare neoplasm arising in children and young adults (mean age 17 years)

No gender predilection

Typical locations: superficial cortical regions of the frontoparietal lobe and the temporal lobes including the hippocampus and parahippocampal gyri

Pharmacoresistant epilepsy

Complex partial seizures in temporal lobe tumors

Characterized by slow growth

Treatment: resection, often with good outcome

Well demarcated, solid hyperintense mass on MRI (T2 and FLAIR) images; nonenhancing; causes little mass effect

Stalklike extension of the tumor to ventricular surface

Expansion of involved areas of brain tissue

Monomorphous, bipolar cells with elongated nuclei having distinctly speckled chromatin

Angiocentric pattern produced by circumferential or longitudinal orientation of tumor cells along large and small blood vessels

Radial perivascular arrangements of tumor cell processes may resemble that of conventional ependymoma or even astroblastoma

Mitoses rare or absent; no necrosis or microvascular proliferation

Subpial accumulation of tumor cells may mimic infiltrating glioma

Tumor cells immunoreactive for GFAP, S-100, and vimentin

Dotlike, microlumen pattern of immunoreactivity for epithelial membrane antigen

Negative for neuronal lineage antigens

Ki-67 (MIB-1) labeling indices usually low (1% to 5%)

Ultrastructure: microlumina filled with microvilli or cilia and intermediate cell junctions