Vol. 7, Issue 2, Part B (2025)

Introduction: Fetus in fetu (FIF) is an anomaly in embryonic development where a fetus is enclosed within the body of its twin. This anomaly is estimated to occur in 1 out of 500,000 live births. Between 1999 and 2013, 95 cases have been reported in the literature. The objective is to present this case of an atypical abdominal teratoma and demonstrate the importance of considering the diagnosis when encountering any abdominal mass in children.
Patient and Observation: A 6-month-old female infant, weighing 6.8 kg, was admitted to the pediatric surgery department at Donka National Hospital for an abdominal mass displacing the right kidney, spleen, pancreas, mesentery, and digestive loops. The mass, which contained bone structures, pelvis, hip, limbs, and teeth, was diagnosed via computed tomography. The mother had attended all prenatal consultations, and the pregnancy proceeded normally to term without any prenatal diagnosis, and the delivery was uneventful. After clinical, biological, and radiological investigations, the diagnosis of a mature abdominal teratoma was considered. During surgery, a large right retroperitoneal fetal mass was discovered. A surgical treatment with complete open resection was performed. The postoperative course was uneventful, and the patient was discharged on the sixth day.
Conclusion: Fetus in fetu is considered a benign condition, whereas the potentially malignant characteristics of the teratoma are the basis for discussion. This may constitute a difference in follow-up and treatment. Although there is a consensus on the benign nature of FIF, it is necessary to completely remove the mass, and periodic hormonal and ultrasound monitoring in the postoperative period constitutes an appropriate approach.