Astrocytoma

Findings:
An exophytic, strongly enhancing intraaxial mass is present in the brainstem at the level of the midbrain, projecting into the posterior third ventricle, which causes obstructive hydrocephalus by compression and/or invasion of the cerebral aqueduct.

Differential Diagnosis:
choroid plexus papilloma, ependymoma, intraventricular meningioma, pineal region tumor (germ cell, pineoblastoma, pineocytoma), astrocytoma (no distinguishing features in this particular case).

Discussion:
1993 WHO classification:
 grade I
    -JPA, PXA, SGCA, ganglioglioma, meningioma
 grade II
    -diffuse astrocytoma, HPC
 grade III
    -anaplastic astro, HPC
 grade IV
    -GBM

astrocytoma
   -70% of all gliomas
   -low grade: children and adults 20-40, no necrosis or neovascularity, cystic, calcification 20%, fysr 33%
   -high grade:>40, necrosis, neovascularity, hemorrhage. median srv 8 mos.
   -spread- natural passages, subpial, subependymal, WM tracts, may cross meninges
   -GBM may be better circumscribed microscopically than lower grade astro
   -necrosis separates GBM from anaplastic astro

GBM
   -most common glioma, peak 45-55yrs., M>F, 10% 2ysr
   -deep frontal white matter most common, temporal lobe and basal ganglia
   -expansile, necrosis, ring enhancement, edema, +/- flow voids
   -well circumscribed gross appearance with wide invasion microscopically
   -T2 hyperintensity in corpus callosum = tumor spread, not edema
 
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