Supratentorial ependymoma

Large mass centered on the anterior corpus callosum extending into both frontal lobes. It has cystic and enhancing components with a small focus of calcification. Superiorly there is a small a fluid- fluid level suggestive of intratumoral hemorrhage. Anterior horns of the lateral ventricles are effaced but there is no hydrocephalus.

Large heterogeneous frontal mass, associated with the inferior falx with at least a large component being extra-axial in location (CSF cleft, peripheral vessels and buckling of adjacent cortex). This is not, however, true around the entirety of the mass, and an exophytic parenchymal tumor remains a possibility.

Large, central, lobulated solid component enhances heterogeneously and contains regions of susceptibility artefact. Peripherally enhancing cystic/ necrotic components contain fluid levels with susceptibility artefact in keeping with blood product. Further peritumoral cysts demonstrate incomplete FLAIR suppression.

Marked mass effect with near complete effacement of the anterior horns of the lateral ventricles, focal inferior buckling of the corpus callosum anteriorly, and partial effacement of the third ventricle and suprasellar cistern. Posterior fossa CSF spaces remain intact. MRS demonstrates elevated choline, and probable glutamine/glutamate as well as lipid-lactate peaks. NAA is, importantly, present as is creatine. Cerebral blood volume is elevated. Moderate diffusion restriction (~1000 x 10^-6 cm^2/s). Allowing for artefact, major dural venous sinuses including the superior sagittal sinus appear to enhance normally. No bony abnormality is seen.

Conclusion: Large, heterogeneous frontal mass has a large extra-axial component, but not definitely entirely extra-axial. Although at first a meningioma, or perhaps a hemangiopericytoma, were the favored diagnoses, the presence of tumoral hemorrhage and moderate NAA on MRS makes this unlikely. The differential, therefore, includes an exophytic parenchymal/cortical tumor such as a pilocytic astrocytoma, pleomorphic xanthoastrocytoma, ganglioglioma or even parenchymal ependymoma. This is very unlikely to represent a high-grade diffuse glioma.

The patient went on to have surgery.

Histology

MICROSCOPIC DESCRIPTION:

The sections show features of a moderately cellular glial tumor. The tumor cells form sheets and there are widely distributed perivascular pseudorosettes, where the tumor cells surround central blood vessels. No thick radiating astroblastic type cytoplasmic processes are seen. A few blood vessels are hyalinised. The background is fibrillary. The tumor cells have angulated and hyperchromatic nuclei. Some fascicular arrangement is noted, with a tanycytic-like pattern. No Rosenthal fibers or eosinophilic granular bodies are noted. There are 2 mitoses per 10 high-power fields. No microvascular proliferation is seen. There are occasional foci of non-palisaded necrosis where there is fibrinoid material and some neutrophils. No oligodendroglial component is noted. The features are those of ependymoma.

The tumor cells are GFAP, CD99 and focally p53 positive. The topoisomerase index is about 5%. IDH1-R132H immunostain is negative. MGMT is positive (likely unmethylated). ATRX shows no loss of staining (non-mutated). EMA shows scattered positive cells with a perinuclear dot pattern of reactivity. A few rudimentary ependymal canal-like structures are noted. NeuN and synaptophysin are negative, excluding neurocytoma.

FINAL DIAGNOSIS: Ependymoma (WHO Grade II).