Malignant evolution of childhood chiasmal pilocytic astrocytoma.

A 27-year-old obese mentally retarded woman showed progression of antisocial behavior with periodic somnolence 18 years after biopsy and irradiation of a large pilocytic astrocytoma of the chiasm and adjacent structures. Visual function, although impaired, had not changed during the long period of postoperative observation. Before she died, the tumor showed angiographic and histologic features of malignant glioma, but neuroradiologic and neuropathologic studies did not establish conclusively that it involved new areas of the brain. This report documents a rare case in which an irradiated childhood optic glioma underwent delayed malignant evolution.