Two Cases of Fetus in Fetu Diagnosed with Prenatal Ultrasonography

Fetus in fetu is a poorly understood and rare congenital malfomation. This is a rare form of monozygotic twin that asymmetric twin becomes internalized in the other twin thus acting endoparasitically. Fetus in fetu can be distinguised from teratoma, because of vertebral column, skeletal axis, and well-differentiated internal organs. We present the findings in the two cases of fetus in fetu that were diagnosed with prenatal ultrasonography. After birth, we removed fetus-like structures and confirmed by pathologic examination. Fetus-like structures were consisted of vertebral column, extremities, and other well-developed internal organs.