Twin fetus in fetu with immature teratoma: a case report and review of the literature.

Fetus in fetu is an extremely rare condition in which a fetus or fetus-like structure with a vertebral axis is seen in the body of its twin. This paper presents a case of fetus in fetu in a two- day-old female newborn who was referred for an abdominal mass, biliary vomiting, and feeding intolerance. After plain abdominal X-ray and ultrasonography, the patient underwent abdominal surgery with the primary diagnosis of teratoma or fetus in fetu.