First Case Report of Adnexal Fetus in Fetu.

There is an ambiguous and controversial line between fetiform teratoma and fetus in fetu (FIF) as differential diagnoses of a fetiform mass. Classically, the presence of vertebral column often with a relatively proper arrangement of other organs around the central axis favor the diagnosis of FIF over teratoma. Based on previously proposed criteria and the presence of vertebral organization in the radiological and histopathological assessment of the fetiform mass, we present an extremely rare case of adnexal FIF in a 10-year-old girl presenting with acute abdominal pain. Whether FIF and fetiform teratoma are one entity or two, clinical discrimination for the choice of treatment seems to be unnecessary and the patient should be clinically followed for the probable malignant potential. [ABSTRACT FROM AUTHOR]