Fetus in fetu or fetiform teratoma? Report of two cases

Abstract

Fetus in fetu is a rare congenital entity in which a deformed parasitic twin develops within the body of a living newborn or a child. Meanwhile, fetiform teratoma is a rare congenital disorder with high degree of organoid differentiation resembling fetus in fetu. We present two cases of the rare entities with two unusual locations. A 1-week-old baby boy with a large anterior abdominal mass underwent CT-scan. A large mass containing pelvic bones, femora, tibia, fibula, fused kidneys, urinary bladder, hepatic parenchyma, brain tissue and spinal cord was noted in the anterior abdominal wall. The liver parenchyma of the host twin was fused with the hepatic parenchyma of the parasitic twin. Another 6-month-old baby girl with a large lumbar lump underwent ultrasonography, CT-scan and surgery. On imaging, a sac-like structure was noted in the lumbar region containing bowel segments, mesentery-like structure and few lymph nodes. Both cases are rare congenital anomalies and are a diagnostic challenge. It has been described that the presence of axial skeleton and limb buds differentiates the fetus in fetu from the fetiform teratoma, therefor, the first case was diagnosed as fetus in fetu and the latter one as fetiform teratoma.

Keywords

• Fetiform teratoma
• Fetus in fetu
• Case report