Primary Mediastinal Pure Seminomatous Germ Cell Tumor (Germinoma) as a Rare Cause of Precocious Puberty in a 9-Year-Old Patient.

Less than 5%-7% of germ cell tumors are extragonadal, with the central nervous system being the most common location in children, followed by retroperitoneum and mediastinum. Only 10% of mediastinal tumors are malignant and one-third of these are pure seminomas (germinomas). We report the case of a 9-year-old boy with development of secondary sexual characteristics. Beta-human chorionic gonadotropin was elevated and a mediastinal mass was found. Final histology showed a pure seminomatous germ cell tumor. To our knowledge, this is the first report of a boy with precocious puberty secondary to a mediastinal germinoma.