Malignant transformation of an optic pathway glioma without prior radiation therapy.

Optic pathway gliomas (OPGs) arise from the optic nerves, optic chiasm, and/or hypothalamus and most commonly occur in childhood. Although these tumors can be quite challenging to manage, they are typically low-grade astrocytomas histologically, most commonly pilocytic astrocytomas. The few previously reported cases of malignant degeneration of an OPG occurred after external beam radiation therapy. The authors report the first case in the English literature of an OPG that transformed from a low-grade astrocytoma, with features most consistent with a pilocytic astrocytoma, to a malignant glioma without any exposure to radiation therapy.