Fetus in Fetu: Is it a Baby Inside a baby?

Abstract

Fetus in Fetu is a rare congenital anomaly in which monozygotic twin is incorporated into its sibling during development. It is a lesser known disease even in the medical community as less than 200 cases have been reported. Some theories have been proposed regarding the pathogenesis of fetus in fetu and clinical manifestations of fetus in fetu vary. It should be differentiated from teratoma which has no axial arrangement and has got definite malignant potential. Herein, we describe a 5month old boy with an abdominal mass. After ultrasound and CT scan, provisional diagnosis of Fetus in fetu causing bilateral moderate hydroureteronephrosis was made. Elective laparotomy revealed a well encapsulated retroperitoneal mass which was successfully excised. Complete excision of fetus in fetu is curative. The rarity of this case is the reason why we deem our case reporting.

Fetus in fetu: use of intraoperative ultrasound for safe excision of a rare entity

“…In order to diagnose FIF, pathological evaluation must identify a mass containing vestigial remnants enclosed by a distinct sac partly composed of skin, grossly recognisable body parts such as osseous structures, and a few blood vessels. FIF can be differentiated pathologically from teratoma by identifying body parts such as vertebral segments and soft tissue and limbs of equal maturity while teratoma is composed of disorganised pluripotent cells without identifiable body parts 11. A vertebral column is identified in 76% of cases and limbs are seen in 83% of cases 2 9.…”