Atypical basal ganglia germinoma presenting as cerebral hemiatrophy: diagnosis and follow-up with C-11-methionine positron emission tomography

Some basal ganglia germinomas are difficult to diagnose in early stage of disease due to vague initial presentation without discernable mass lesion on brain imaging. We performed this study to determine the usefulness of C-11-methionine positron emission tomography (MET PET) for the diagnosis and monitoring of disease activity. MET PET was performed in three consecutive patients; they presented with cerebral hemiatrophy without definite mass lesions on brain image. The maximum standard tracer uptake values (max SUVs) were calculated and used for the quantitative evaluation of the abnormal MET uptake. A pathological diagnosis was made after stereotactic biopsy using MET PET/computed tomography. The max SUVs significantly decreased after treatment. Basal ganglia germinoma should be considered in the differential diagnosis of patients with progressive hemiparesis and hemiatrophy on magnetic resonance imaging. The MET PET was useful for diagnosis, and it can be valuable in evaluation of treatment effects and monitoring for tumor recurrence.