Radiation therapy and malignant degeneration of benign supratentorial gangliogliomas

OBJECTIVE: Gangliogliomas are indolent tumors comprised of neoplastic glial and neuronal cells. Benign lesions tend to be associated with long survival unless the tumor degenerates to a histologically malignant form. This study reviews four cases of histologically proven benign ganglioglioma that later demonstrated malignant features within the glial component of the tumor. Features common to each case are analyzed, and similar cases from the literature are reviewed. METHODS: The records of 42 supratentorial gangliogliomas operated on at our institution since 1985 were reviewed. Special attention was paid to histological characteristics, use of adjuvant radiotherapy, time to tumor recurrence, and histology of the recurrent tumor. RESULTS: Of the 42 cases of gangliogliomas, 29 were initially histologically benign. Of these 29, 14 received postoperative radiation therapy and 14 did not; it was unclear whether one patient received adjuvant radiotherapy, and this patient was excluded from further analysis. Four benign gangliogliomas exhibited malignant degeneration of the glial component. These four all occurred in patients who had undergone postoperative irradiation. The time to identified histological change within recurrent tumors averaged 65 months (range, 22-144 mo). CONCLUSION: All of the benign gangliogliomas undergoing malignant change had postoperative radiation therapy as a common feature. This represents a potential correlation that requires further study.