Germ-cell tumours of male ussually arise from the testis. However, in 2-5% of the cases, they also occur outside of the testis as a primary site without evidence of testicular primary tumour. This infrequent entity often appears in the body midline, predominantly in mediastinum and retroperitoneum. Mediastinal germ-cell tumours (MGCT) shall be included in the differential diagnosis of any mediastinic tumour of unknown origin. An accurate diagnosis is essential, due to the fact that these tumours are curable with chemotherapy. The histopathologic and clinical features, and its differences with germ-cell tumours from testicular origin are revised in this article.