Ependymoma (typical, WHO 2000 Grade II)

General: Slow growing tumor of children and young adults (with cases reported from age 1 month to 81 years) originating from the wall of cerebral ventricles or spinal canal, composed of neoplastic ependymal cells. Accounts for 3~9% of all neuroepithelial tumors, 6~12% of all intracranial tumors in children, and ~30% of all intracranial tumors in children < 3 years old. Accounts for ~55% of spinal gliomas, making it the most common neuroepithelial neoplasm of the spinal cord. Spinal cord location has a second peak in the 30-40 year old age group.

Most commonly develop in the posterior fossa (fourth ventricle) or spinal cord, then the lateral ventricles and third ventricle. Supratentorial parenchymal ependymomas have been reported outside the ventricular system, possibly originating from embryonic ependymal remnants, and extremely rare extraneural ependymomas have been reported in the ovaries, soft tissues, mediastinum, and sacrococcygeal area.

There is an increased incidence in neurofibromatosis Type 2 patients.

Prognosis is related to location (spinal > supratentorial > posterior fossa), Ki-67 > 4%, and areas of hypercellular poorly differentiated tumor.

There are several variants, as well as several additional distinct types (See below).

Neuroimaging: On gadolinium-enhanced MRI's ependymomas usually appear as well-circumscribed lesions with varying degrees of contrast enhancement. Ventricular or brain stem displacement and hydrocephalus are common features. Supratentorial tumors may have cystic components, and may be difficult to distinguish from other glial entities in the presence of infiltration. Intratumoral hemorrhage and extensive calcification are occasionally seen.

Gross: Generally well demarcated and extend into ventricular space, though may appear invasive. Usually soft, grey-red tumors, some of which exhibit a cystic component, necrotic or hemorrhagic foci.

Microscopic: Well-delineated, moderately cellular glioma with monomorphic nuclear morphology. Key features are perivascular pseudorosettes and ependymal rosettes. Mitoses are rare or absent, and occasional non-palisading foci of necrosis may be seen (many mitoses and/or extensive necrosis may represent a different distinct type, such as anaplastic ependymoma). Regressive changes include areas of myxoid degeneration, hemorrhage, calcifications, and possibly even foci of cartilage or bone formation.

Stains:

• Positive: GFAP+, S100+, vimentin+, EMA+, CKC+/- focally, Ki-67 <= 4%, nestin+
• Negative: synaptophysin-
• Suggested, focused panel: CKC, EMA, GFAP, Ki-67, S100, vimentin, synaptophysin

Molecular & Cytogenetics:

• 30% incidence of chromosome 22 aberrations (monosomy, deletions, or translocations).
• Several other variants associated with ependymomas, but true significance isn't clear.

((())) WHO 2000

Images:

Cases:

Variants of typical:

• Cellular ependymoma
• Papillary ependymoma
• Clear cell ependymoma
• Tanycytic ependymoma
• Very rare: Ependymoma with lipomatous differentiation, giant cell ependymoma of the filum terminale, extensive tumor cell vacuolation, melanotic ependymoma, signet ring cell ependymoma, and ovarian ependymoma.

Classified as different types:

• Anaplastic Ependymoma WHO 2000 Grade III
• Myxopapillary Ependymoma WHO 2000 Grade I
• Subependymoma WHO 2000 Grade I