Extragonadal yolk sac tumor following congenital buccal mature cystic teratoma.

Yolk sac tumor (YST) and teratoma both categorized as germ cell tumor (GCT). YST shows preferential differentiation toward yolk sac structures, while teratoma consists of tissues that originate from at least two embryonic germinal layers. Extragonadal location of YST is rare, whereas extragonadal teratoma is majority presented in nasopharynx area. Mature teratoma tends to be benign although some malignant transformation can occur. Recurrence of teratoma was reported mostly in the case of immature teratoma. YST occurrence after removal of mature teratoma is never reported. It is extremely rare for a second GCT to occur at the same site and with a different histological type. We herein report a case of a female infant presented with YST following a congenital buccal mature teratoma.