Gangliogliomas generally behave as benign indolent
tumors. However,
gangliogliomas undergoing malignant transformation have also been reported. The molecular basis for the malignant transformation of
gangliogliomas remains unclear. We describe a case of
ganglioglioma, which had transformed to
glioblastoma after the gross total resection of the original
tumor, in a 4-year-old girl. The present case is unusual in four aspects: (i) it arose from a low-grade
ganglioglioma in the absence of previous radiation or
chemotherapy, which is the fourth reported case; (ii) the original
tumor showed a high proliferative index on flow cytometry but a low Ki-67 labeling index, implying that the application of flow cytometry might play a certain role in predicting
biological and clinical behavior of low grade
gangliogliomas; (iii) p53 mutation and deletion appeared in the secondary
glioblastoma, which was not shown in the original well-differentiated
ganglioglioma; and (iv) the transformed
glioblastoma showed p16 inactivation detected by methylation and deletion, which are relatively uncommon genetic events in secondary
glioblastomas. This is the first report of a genetic alteration in
glioblastoma arising from a well differentiated
ganglioglioma prior to radiation or
chemotherapy. Based on the above findings, irrespective of
radiotherapy or
chemotherapy, rare recurrence of malignant evolution, especially
tumors of high S-phase fraction on flow cytometry, warrants long-term follow-up, even in a well-differentiated
ganglioglioma.