ABSTRACT
Gliomas account for 70% of all primary brain tumors, the vast majority (about 80%) of which are of astrocytic origin. Most astrocytic tumors are so-called diffuse astrocytomas, because of their infiltration of adjacent and distant brain structures, regardless of grade. Diffuse astrocytoma represents a continuum, with a grading dependent on the presence or absence of anaplastic features. According to the World Health Organization (WHO) classification (1), low grade astrocytoma (grade II) is defined as an astrocytic neoplasm, with a high degree of cellular differentiation, slow growth, and diffuse infiltration of neighboring brain. The tumor is considered an anaplastic astrocytoma (or grade III) if focal or dispersed anaplasia is present, with increased cellularity, distinct nuclear atypia and marked mitotic activity. The presence of endothelial proliferation and necrosis is the hallmark of the glioblastoma multiforme (GBM) (grade IV). This tumor, with its median survival of 9 to 12 months makes up 60% to 80% of the diffuse astrocytic tumors.
