Intracranial tumors comprise approximately 2% of all adult
cancers, but form a larger fraction within the group of
childhood tumors. Gliomas account for approximately 60% of all
intracranial tumors and are classified according to the
suggested cell of origin, differentiation and malignancy grade.
The prognosis for high-grade gliomas is poor due to limited
possibilities of curative treatment. Gliomas are tumors of
neuroepithelial tissue and comprise a complex and heterogeneous
group of tumors representing counterparts to various normal
inhabitant cells of the central nervous system (CNS). The most
common form of glioma is astrocytoma, representing approximately
one third of all gliomas. Astrocytomas are defined based on
morphological features such as cellularity, nuclear atypia,
mitotic rate, endothelial proliferation and necrosis, and
assigned to grades I-IV according to the current WHO
classification system. These include pilocytic astrocytoma
(Grade I), astrocytoma (Grade II), anaplastic astrocytoma (Grade