Glioblastoma multiforme pathophysiology

Pathogenesis
Glioblastomas multiforme are characterized by the presence of small areas of necrotizing tissue that is surrounded by highly-anaplastic cells (pseudopalisading necrosis). This characteristic, as well as the presence of hyperplastic blood vessels, differentiates the tumor from Grade 3 astrocytomas, which do not have these features. Although glioblastoma multiforme can be formed from lower-grade astrocytomas, post-mortem autopsies have revealed that most glioblastomas multiforme are not caused by previous lesions in the brain

Unlike oligodendrogliomas, glioblastomas multiforme can form in either the gray matter or the white matter of the brain; but most GBM arises from the deep white matter and quickly infiltrate the brain, often becoming very large before producing symptoms. The tumor may extend to the meningeal or ventricular wall, leading to the high protein content of cerebrospinal fluid (CSF) (> 100 mg/dL), as well as an occasional pleocytosis of 10 to 100 cells, mostly lymphocytes. Malignant cells carried in the CSF may spread to the spinal cord or cause meningeal gliomatosis. However, metastasis of GBM beyond the central nervous system is extremely rare. About 50% of GBM occupy more than one lobe of a hemisphere or are bilateral. Tumors of this type usually arise from the cerebrum and may exhibit the classic infiltrate across the corpus callosum, producing a butterfly (bilateral) glioma.

The tumor may take on a variety of appearances, depending on the amount of hemorrhage, necrosis, or its age. A CT scan will usually show a nonhomogeneous mass with a hypointense center and a variable ring of enhancement surrounded by edema. Part of a lateral ventricle is usually deformed, and both lateral and third ventricles may be displaced.