Oligodendroglioma: diagnosis and prognosis.

Oligodendrogliomas represent only 4% to 7% of intracranial gliomas, but accurate diagnosis of this neoplasm is important. They occur almost exclusively in the cerebral hemispheres and are most common in adults in middle life. Although classically associated with calcifications, these may be present in only 50% of cases. Special diagnostic techniques, including touch imprint preparations, electron microscopy, and immunohistochemistry can be useful in diagnosis. Grading systems correlating with prognosis have not been well established, but two recent careful clinical and pathologic studies have provided concrete and apparently valid criteria for grading. There is some evidence that radical surgical excision improves survival. Most patients receive postoperative radiation therapy. Prospective controlled therapeutic trials are lacking, however.