Fetus in fetu in the liver: case report and review of the literature.

Fetus in fetu is an extremely rare cause of abdominal mass in infancy, which most likely arises from inclusion of monozygotic diaminiotic twin. This entity is distinguished from teratoma by the presence of vertebral axis with limb bud or any other appropriately situated bones or organs. It occurs predominantly in the upper retroperitoneum, less frequently in the pelvis and ileal mesentery. Unlikely sites of occurrence such as the cranial cavity and the scrotum have been reported. In the present case the sac that contains the fetus was found in the right lobe of the liver, a site which has not been reported before. To our knowledge, and as far as the available literature is concerned, we believe this is the first report of such a case.