Cerebral hemiatrophy with superficial siderosis and PLEDs due to a germ cell tumor of the basal ganglia.

The diagnosis of basal ganglia germ cell tumors may be delayed due to slow progression and minimal early changes on magnetic resonance imaging (MRI). The cystic nature of some tumors may lead to non-diagnostic biopsies. We describe the clinical, imaging, laboratory, and postmortem findings of a basal ganglia germ cell tumor in a 19-year-old man. Clues to an early antemortem diagnosis based on MRI findings and determination of tumor markers are discussed. An early diagnosis and accurate characterization of basal ganglia germ cell tumors is essential for optimal therapy. The presence of cerebral hemiatrophy and hemorrhagic or cystic components is suggestive. Measurement of serum and cerebrospinal fluid markers such as human chorionic gonadotropin may suggest the diagnosis.