[Retroperitoneal teratoma. A problem in pediatric urology].

We report about diagnosis and therapy of a retroperitoneal teratoma in a six years old boy. Further we discuss the histogenetical origin as well as the histological classification. Considering other localisations, teratomas of the retroperitoneum are relatively (4%) rare. Most teratomas are diagnosed at school-age either coincidently or because of a mass lesion. Size and localisation of the tumor do not give any information about its nature. Even with negative tumor markers (alpha1-fetoprotein, beta-HCG) the tumor should be considered malignant until histology proves the contrary. Due to these facts a careful en bloc extirpation and a thorough histological examination of the tumor are always necessary.