Retroperitoneal giant tumor formed by migrating polyembryoma with numerous embryoid bodies from an ovarian mixed germ cell tumor.

We report on a very rare case of retroperitoneal tumor formed by migrating polyembryoma with numerous embryoid bodies from an ovarian mixed germ cell tumor. It was successfully removed combined with artificial replacement of the aorta following chemotherapy. We also discussed the fate of embryoid bodies following metastasis or chemotherapy.