Glioma

Definition

Gliomas are the most common primary tumor of the CNS, accounting for approximately 75% of malignant adult primary CNS tumors (Kleihues and Cavenee 2000). They arise from glial cells and their precursors within the central nervous system. Gliomas are most commonly found in the white matter of the cerebral hemispheres but can also invade or infringe on gray matter. Known for their potential for proliferation, gliomas can also invade the spinal cord. In addition to abnormal signal seen on CT, MRI, or PET, gliomas also invade normal-appearing parenchyma that is peripheral to the abnormal signal and may grow extensively before symptoms become apparent. However, radiotherapy targets only the 2 cm bed around the tumor, and thus tumor recurrence is common. The relative subtlety of early gliomas is presumable because the invaded normal-appearing brain tissue can still function, and a significant increase in symptoms is often found after surgical resection due to the removal of this...