Mixed testicular germ cell tumor in an adult with cryptorchidism and Down's syndrome.

We here present a case of mixed testicular germ cell tumor in an adult with cryptorchidism and Down's syndrome. A 20-year-old Japanese man with a mass in the left inguinal region underwent orchidectomy as a left testicular tumor was suspected. Histology showed a mixed germ-cell tumor with embryonal carcinoma and yolk sac tumor with syncytiotrophoblastic giant cells occurring in a cryptorchid testis. Chromosomal analysis of peripheral lymphocytes disclosed a karyotype of 47,XY,+21[20]. Our case provides further evidence that these three conditions-Down's syndrome, cryptorchidism and testicular germ cell tumor-may be closely associated. To our knowledge this is the first case of mixed germ cell tumor arising in a patient with Down's syndrome and cryptorchidism.