A Case of Klinefelter Syndrome Associated with Mediastinal Germ Cell Tumor Presenting with a Prominent Gynecomastia

Abstract

We described a 13-year-old boy with Klinefelter syndrome associated with a mediastinal germ cell tumor. He initially presented with_ ;a prominent gynecomastia, which might be considered to be a symptom of Klinefelter syndrome. The serum levels of AFP and β-hCG were extremely elevated. The germ cell tumor was treated with chemotherapy and total resection of the tumor. After he achieved complete remission, his gynecomastia was improved. The gynecomastia might be associated with not only Klinefelter syndrome but also the β-hCG-producing germ cell tumor.