Germinoma: Unusual Imaging and Pathological Characteristics. Report of Two Cases.

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Primary germ cell neoplasms of the central nervous system typically develop as midline mass lesions during the first three decades of life. The authors present two cases with atypical clinicopathological features that stimulate discussion on the diagnosis and management of these tumors. The first patient was an 11-year-old boy of Japanese-American heritage who presented with a 6-month-long history of cognitive decline, difficulty swallowing, unsteady gait, and intermittent right-sided posturing. The initial magnetic resonance (MR) image of the brain displayed a mildly increased T2 signal in the cerebral peduncles, putamen, and globus pallidus bilaterally. Follow-up MR images showed an increase in the T2 signal abnormality in the left basal ganglia. The second patient was a 10-year-old Caucasian boy who presented with diabetes insipidus and subsequently displayed progressive fatigue, involuntary eye and mouth movements, and obsessive-compulsive behavior. An MR image demonstrated signs of mineral deposition and foci of increased T2 signal in both basal ganglia. Follow-up MR images demonstrated a progressive increase in the T2 signal (which was then located within the mesial temporal lobe). A biopsy performed on the left thalamic lesion in the first patient revealed a germinoma. The patient was treated with chemotherapy and died 2 years later. The second patient underwent a lumbar puncture, which demonstrated an elevated level of beta-human chorionic gonadotropin. Despite the lack of a mass on MR images in this child, the need for a tissue diagnosis prompted the authors to perform an anterior temporal lobectomy. The diagnosis of diffuse germinoma was confirmed, and the patient was treated with adjunctive chemotherapy. Although uncommon, germ cell tumors can present outside the midline and exhibit a multifocal growth pattern.