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Ependymoblastoma

Sheets of immature-looking cells with ependymoblastic rosettes

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Definition

High grade (WHO grade IV) embryonal tumor of infancy and early childhood with characteristic ependymoblastic rosettes.

Clinical Features

High-grade
Infancy and early childhood
Disseminated CSF-borne metastasis is common

Gross Pathology

Usually paraventricular localization deep within cerebral hemispheres
May arise in posterior fossa1,2
Other presentations:
- primary leptomeningeal 3
- extradural sacrococcygeal4 associated with elevated serum α-fetoprotein

Histopathology

Densely populated
Small, monomorphous cells:
- in sheets or broad, anastomosing cords punctuated by ‘ependymoblastic’ rosettes
- lack PAS-positive basement membranes of medulloepitheliomatous arrays
- distinguished from rosettes of mature ependymal type by:
  - multilayered stratification of encircling nuclei
  - manifest proliferative activity
    - mitoses often in juxtaluminal position
- no or only poorly developed perivascular pseudorosettes
Necrosis common:
- not associated with cellular palisading
Generally no microvascular proliferation
Ultrastructurally:
- rosette-forming elements:
  - ependymal nature
  - elaborate apical cell junctions, microvilli, and cilia1,4,5
  - may exhibit focal GFAP immunolabeling 1,5

Diagnosis

By definition, devoid of medullary epithelial structures and incapable of divergent neuronal differentiation

Differential Diagnosis

Select up to 2 differential diagnoses to compare with Ependymoblastoma

Anaplastic ependymoma

Prognosis

Usually fatal within 1–2 years of diagnosis

References

1 Cruz-Sanchez FF, Haustein J, Rossi ML, Cervos-Navarro J, Hughes JT. Ependymoblastoma. A histological, immunohistological and ultrastructural study of five cases. Histopathology. 1988;12:17–27.

2 Mork SJ, Rubinstein LJ. Ependymoblastoma. A reappraisal of a rare embryonal tumor. Cancer. 1985;55:1536–1542.

3 Wada C, Kurata A, Hirose R, Tazaki Y, Kan S, Ishihara Y, et al. Primary leptomeningeal ependymoblastoma. Case report. J Neurosurg. 1986;64:968–973.

4 Murphy MN, Dhalla SS, Diocee M, Halliday W, Wiseman NE, de Sa DJ. Congenital ependymoblastoma presenting as a sacrococcygeal mass in a newborn. An immunohistochemical, light and electron microscopic study. Clin Neuropathol. 1987;6:169–173.

5 Langford LA. The ultrastructure of the ependymoblastoma. Acta Neuropathol (Berl). 1986;71:136–141.

Last updated: 14 Feb 2006