Clinicohistological study of oligodendroglioma and oligoastrocytoma.

The clinical and histological characteristics of oligodendroglioma and oligoastrocytoma were investigated in patients, mainly adults with supratentorial tumors, who were treated with surgery and radiotherapy, and with chemotherapy for recurrent, anaplastic tumors, or both. The median survival time was 13.2 years for oligodendroglioma (four patients), 12.7 years for anaplastic oligodendroglioma (five patients), 13.5 years for oligoastrocytoma (seven patients), and 4.8 years for anaplastic oligoastrocytoma (four patients). Two of three recurrent oligodendrogliomas and two of two recurrent oligoastrocytomas showed malignant transformation. Minigemistocytes were sometimes recognized in recurrent tumors and had a sinister prognosis. Oligodendroglioma and oligoastrocytoma may transform into each other at recurrence.