[Fetus in fetu: a case report].

Fetus in fetu is an abnormality secondary to abnormal embryogenesis in a diamniotic, monochorionic pregnancy. It is a rare pathological condition and fewer than 100 cases have been reported in the literature. We report a neonatal case which occurred in a girl who had been hospitalized since birth because of an abdominal mass. A conventional radiograph of the abdomen revealed a right mass containing calcifications, which displaced intestinal structures to the left. Abdominal ultrasonography and CT scan revealed a vascular and heterogeneous mass that contained numerous calcifications. The diagnosis of teratoma was suspected. After surgical excision, macroscopic and pathologic examination confirmed the diagnosis of FIF.