Gliomatosis cerebri is a diffuse astrocytic neoplasm, characterized by diffuse brain infiltration involving more than two lobes, and often extending bilaterally and into infrantentorial structures. Gliomatosis cerebri corresponds to WHO Grade III astrocytoma.
Peak incidence is between 40 and 50 years. Both genders are equally affected.
The primary nosological characteristic of gliomatosis cerebri is its diffuse growth pattern. When lesions involve the cerebral hemispheres, the centrum semiovale is always affected, while infiltration of the Cerebral Cortex occurs in only 19% of all cases.
The most frequent clinical features are corticospinal tract deficits, dementia, headaches, seizures, Cranial nerve deficits, increased Intracranial Pressure and papilledema, and spinocerebellar deficits.
FLAIR and T2-weighted MR imaging demonstrate a diffuse, hyperintense Lesion with widespread brain infiltration. The affected structures appear enlarged. Enhancement is unusual, though a more solid neoplastic component may at times be present (see below).
Type I gliomatosis is the classical lesion characterized by diffuse neoplastic growth and enlargement of the involved structures, without the formation of a circumscribed Tumor mass. Type II gliomatosis is associated with the presence of an obvious neoplastic mass in addition to the diffuse tumor.
Gliomatosis cerebri is composed of infiltrating neoplastic astrocytes with increased cellularity, nuclear atypia and marked mitotic activity. Infiltrating cells often form parallel rows among white matter tracts. GFAP and S-100 are occasionally expressed.
Growth fraction, as determined by the Ki-67/MIB-1 index, is usually intermediate, higher than that for LGG, but lower than that found in GBM
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