Anterior mediastinal cystic seminoma.

Mediastinal cystic seminoma is uncommon; only 17 cases have been reported, most diagnosed postoperatively, without recurrence on follow-up, even without radiotherapy. Here, we report a mediastinal seminoma showing a unilocular cyst with enhancing thickened wall in computed tomography (CT) and septal structures in magnetic resonance imaging (MRI) in a 24-year-old man. Fluorodeoxyglucose (FDG) uptake was not significant. Histopathologically, seminoma cells were found scattered in the cyst wall. Twenty months after resection, the patient's quality of life is good, without chemotherapy or radiation. Cystic seminoma has a good prognosis and complete resection without adjuvant therapy might be sufficient for young patients of reproductive age.