Cystic glioma of the brain stem with prolonged survival.

An unusual case of benign stem glioma with a 15-year survival is presented. In spite of 12 years of clinical quiescence, a focus of the tumor in the upper brain stem was found at necropsy. Morphologically, the tumor was a cystic pilocytic astrocytoma. The few previously reported similar cases in the same location were also associated with a favorable prognosis. It is suggested that, in analogy to the cystic cerebellar and cerebral astrocytomas, there is a group of cystic pilocytic astrocytomas of the brain stem with benign biological behavior.