Mediastinal seminoma occurring in Down syndrome.

The increased incidence of testicular tumor occurrence, especially seminoma, in Down syndrome has been well documented. However, primary mediastinal seminoma occurring in Down syndrome has not been reported. Incidental discovery of an anterior mediastinal tumor was made in a 28-year-old Japanese man with Down syndrome, who had been scheduled for bone marrow transplantation to treat aplastic anemia. Histopathological findings of the resected tumor were typical of seminoma. This case indicates that seminoma can occur in the mediastinum in addition to testis in Down syndrome.