Cellular Ependymoma (WHO 2000 Grade II, Ependymoma variant)

General, Neuroimaging, & Gross: (See also: Ependymoma)

Microscopic: This variant shows conspicuous cellularity without a significant increase in mitotic rate or proliferation index. Pseudorosettes may be inconspicuous and ependymal rosettes may be absent. They lack other properties of anaplastic ependymoma and remain classified as Grade II, variant of typical ependymoma. The relative dearth of typical histologic features may initially leave the differential diagnosis broad and investigated/stained as a small round blue cell tumor.

Stains: Panels depend on age, sex, history, and differentiation of tumor on H & E. Assuming a small round blue cell differential:

• Positive & Negative: (See ependymoma)
• Suggested, focused panel:
  • Pediatric (<20) population: CD45, CD99, CKC, EMA, GFAP, S100, synaptophysin
  • Older (>50) population: CD45, CKC, EMA, GFAP, HMB-45, S100, synaptophysin, (??lobular breast)

((())) WHO 2000

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