Fetus in Fetu: Lessons Learned from a Large Multicenter Cohort Study

Abstract

Introduction Fetus in fetu (FIF) is an extremely rare condition of abnormal twinning during embryogenesis. Most publications are single case reports. We describe the combined experience of four large tertiary referral centers with FIF which were not previously reported or published, and thereby draw conclusions to establish criteria for the workup, diagnosis, and management including intraoperative risk. Materials and Methods A survey was forwarded to a national pediatric surgery group which includes members from all pediatric surgery centers in the country enquiring about unpublished cases of FIF encountered over a 20-year interval. The cohort was analyzed for age of presentation, type of presentation, diagnostic workup, surgical management, and outcome. Results From 1998 to 2018, a total of 10 FIF cases were included in the study. Mean age of presentation was 4 months. Computed tomography and ultrasound were the main preoperative diagnostic modality in our cohort. Resection of the mass was curative in nine cases. Two cases in which the FIF was in direct topographic proximity to the biliary tree suffered severe intraoperative or lethal postoperative complications. Conclusion Complete excision of FIF is the treatment of choice and generally results in excellent long-term quality of life. Mortality is rare and may be associated with biliary involvement and retroperitoneal right upper quadrant location of the FIF tends to be associated with increased risk in excision, and there is also a possible association with the presence of immature elements in the pathology report.

Rare Fetus-in-Fetu: Experience From a Large Tertiary Pediatric Referral Center

“…Once the FIF is diagnosed, surgical treatment is essential, and the prognosis is good after complete resection ( 2 ). The success of the resection is related to the size of the mass, local pressure, intracystic mass bleeding, and other uncertain diagnoses.…”

“…Clinically, fetus-in-fetu (FIF) is a very rare disease ( 1 ) and mostly occurs in neonates, with an incidence of about 1 in 500,000 live births; it is rare in adults ( 2 ). The pathogenesis of FIF is still controversial ( 3 ).…”

“…The diagnosis needs to be differentiated from that of a teratoma. Surgical resection is the main treatment for FIF and can likely offer a cure ( 2 ).…”

A rare case of intrathoracic fetus in fetu / mature teratoma – pathological and imagistic aspects

“…Taher et al [ 2 ] report, although acknowledging the possibility of lacking a well-developed spinal column, states that all of their cases were FIF due to the present of skin, well-formed organs and a vestigial amniotic sac. He also admits a probable reporting bias towards FIF, due to the spectacular component.…”

“…Fetus in fetu (FIF) is a rare congenital anomaly with an incidence of one per 500 000 births [ 1 ]. Taher et al found 224 FIF reported cases [ 2 ]. There are two main theories regarding FIF development: the most prominent is that FIF is in fact a monochorionic twin, which is stopped in evolution and then incorporated into one’s body [ 3 ].…”