The extragonadal germ cell tumors (GCT) are rare neoplasms, which mainly present near the midline, such as mediastinum, retroperitoneal and sacral tail. Intracranial GCTs are very uncommon, with a reported incidence of 0.3% to 3.4% of intracranial neoplasms in Western countries(2), and these mainly occur in the pineal gland and the sella area. However, brainstem GCT is really rare. In this case, MRI shows a mixed signal with mild speckled enhancement involving in thalamus and cerebral peduncle without mass effect. In one report a germinoma in the basal ganglia had a high signal in T1-weighted images, which may be one of the important early signs of GCTs(4). Furthermore, basal ganglia atrophy is the earliest and the most characteristic signs of basal ganglia germinoma(3). Consistent with previous reports(3), the left cerebral peduncle and thalamus also show significant atrophy in this case. Germinomas are highly sensitive to radiation(1). After conventional radiotherapy, the patient has a symptom' improvement and the lesion disappeared in follow-up MRI.
Contributed by Dan Hua Zhu MD, Lin Cai MD, and Zhe Bao Wu MD, PhD