Gliomatosis Cerebri

Definition

Clinical Features

• Rare
• May be extensive at presentation
• Potentially involves entire central neuraxis1
• Clinical course not predictable

Pathogenesis

• Some evidence for a potential cellular origin distinct from that of conventional astrocytomas of diffuse type2

Histopathology

• Large portions of brain:
  • permeated by neoplastic cells:
    • a transformative ‘field effect’ rather than centrifugal spread of a localized glial tumor2,3
  • typically expanded in nondestructive (‘pseudohypertrophic’) fashion without formation of appreciable tumor nodules
• Usually fibrillary astroglial features
• Can be:
  • participating gemistocytic populations4
  • ‘oligodendrogliomatosis’5
• Often emphasized as especially characteristic but not specific or constant:3
  • unusually elongated nuclear profiles in parallel array:
    • due to tumor cell infiltration between compacted nerve fibers
  • tendency to pronounced subpial, perivascular and circumneuronal cellular aggregation

Special Stains and Immunohistochemistry

• Considerable variation in:
  • GFAP expression:
    • sometimes not demonstrable
  • mitotic activity
  • proliferative potential as assessed by MIB-1 (Ki-67) immunolabeling2,6

Diagnosis

• Not a uniform morphologic entity
• Cannot be reliably identified on cytologic or histologic grounds alone
• Formerly reserved for cases examined at autopsy
• Now diagnosed when widespread neuroradiologic abnormalities and biopsy shows diffusely infiltrative glioma

Other Investigations

• MRI:
  • confluent multilobar and bihemispheric zones of T2 signal hyperintensity2,6,7

Differential Diagnosis

Genetics

• Generally support clonal nature of gliomatosis2

Prognosis

• Generally poor
• Death within:
  • 12 months of symptom onset in 52%
  • 3 years of symptom onset in 73%7
• Less aggressive behavior:
  • for some of low histologic grade
  • correlates with limited Ki-67 immunolabeling6
• May be focal or multicentric progression of well-differentiated examples to anaplastic astrocytoma or glioblastoma