Neuropathology of malignant gliomas.

Astrocytomas are the most common primary gliomas, with the highly anaplastic glioblastoma multiforme being the most frequently occurring astrocytoma. Distinctive histological features permit astrocytomas to be graded into levels of anaplasia, and these histological grades correlate with biological behavior and patient prognosis. However, there is also a strong correlation between patient age, tumor grade, and prognosis. More objective indicators of tumor proliferative potential, such as BUdR or Ki-67 LI, are currently being investigated with the hope that these will be a more accurate means of predicting patient survival. Oligodendrogliomas are a much less common primary glioma, with a generally better survival rate than astrocytomas. However, grading systems for oligodendrogliomas are not well defined. For any type of glioma, subsequent surgery after radiation therapy may be required for treatment of therapeutic effects or for therapy planning at recurrence. The histological changes observed in these post-therapy biopsy specimens or resections may be difficult to distinguish from reactive changes that can simulate recurrent tumor and vice versa.