Fetus in fetu: Review of the literature over the past 15 years

A case report of hepatic fetus-in-fetu: Approach to diagnosis

Multiple theories have been proposed about the pathophysiology of Fetus-in-fetu (FIF). The most widely accepted theory is abnormal embryogenesis in diamniotic monochorionic pregnancies, in which a malformed parasitic fetus is found within the body of a twin host. Hepatic FIF has been reported in almost 1% of FIF cases, with only 2 case reports being published in the literature. This article presents the third case report of intrahepatic FIF. Additionally, we review the role of radiology in diagnosing these cases and guiding their proper management. This case report supports the monozygotic twin theory of FIF and the diagnostic dilemma of FIF vs. teratoma can be solved through collaborative work between radiologists and pathologists.

Unusual imaging findings associated with abdominal pediatric germ cell tumors

Germ cell tumors of childhood are tumors arising from germline cells in gonadal or extragonadal locations. Extragonadal germ cell tumors are characteristically located in the midline, arising intracranially or in the mediastinum, retroperitoneum, or pelvis. These tumors are generally easily diagnosed due to typical sites of origin, characteristic imaging findings, and laboratory markers. However, germ cell tumors can be associated with unusual clinical syndromes or imaging features that can perplex the radiologist. This review will illustrate atypical imaging/clinical manifestations and complications of abdominal germ cell tumors in childhood. These features include unusual primary tumors such as multifocal primaries; local complications such as ovarian torsion or ruptured dermoid; atypical presentations of metastatic disease associated with burned-out primary tumor, growing teratoma syndrome, and gliomatosis peritonei; endocrine manifestations such as precocious puberty and hyperthyroidism; and antibody mediated paraneoplastic syndrome such as anti-N-methyl-D-aspartate-receptor antibody-mediated encephalitis. This review aims to illustrate unusual imaging features associated with the primary tumor, metastatic disease, or distant complications of abdominal germ cell tumors of childhood.

Prenatal diagnosis of well-developed fetus in fetu with spontaneous movement in a resource-limited setting: A case report

Fetus in fetu (FIF) is a rare congenital anomaly characterized by the presence of a parasitic monozygotic twin encased within the body of its host twin. Because FIF is asymptomatic throughout pregnancy, it is mainly diagnosed in children with an abdominal mass after birth. In the case reported here, at 38-39 weeks of gestation, a 33-year-old woman (gravida 4, para 3) was referred for routine obstetric ultrasonography. Fluid accumulation was identified along with calcification resembling two well-developed legs and trunk with undifferentiated organs inside. Slight spontaneous movement of the legs was observed. The fetus was delivered based on the presumed diagnosis of FIF. Postnatal sonography and computed tomography (CT) supported the diagnosis. The neonate underwent surgical excision of the tumor and was discharged on the eighth postoperative day. Ultrasound can be used to provide accurate prenatal diagnosis of FIF. Early diagnosis is important to improve outcomes.

Neonatal Sacrococcygeal Fetiform Teratoma Containing Bowel: A Case Report

A fetiform sacrococcygeal teratoma (homunculus) is a highly differentiated subgroup of mature cystic teratoma that resembles a malformed fetus. These tumors originate at the base of the coccyx and may vary in their intrapelvic and extrapelvic extent and location. It is important to differentiate this anomaly from fetus-in-fetu which has a higher degree of structural organization. A 5-day-old neonate presented with a type II sacrococcygeal fetiform teratoma. The mass contained both cystic and solid components. Upon surgical excision and coccygectomy, fully formed bowel was found inside the mass, as well as bones and other well-defined structures. The tumor was confirmed to be fully excised and no malignant or immature features were found on histopathological examination. The patient was last seen growing well with an alpha-fetoprotein of 3.5 μg/L, 14 months after resection.

Fetus-in-Fetu: A Tale of the Trapped Triplets

A 7-day-old male child presented with abdominal distention and jaundice. Radiological investigations revealed an encapsulated sac encasing three fetus-in-fetu (FIF) in the retroperitoneum. Laparotomy revealed a sac occupying almost the whole of the abdomen. The sac was stretching the duodenum and barely visible common bile duct, which were carefully separated. The rest of the bowel was displaced to the left. The sac containing three FIFs was excised intact. One of the fetuses was highly differentiated and had thoracic meningomyelocele, which has never been reported in FIF.

Fetus-in-Fetu: A Differential Diagnosis of Neonatal Fetiform Encysted Abdominal Mass

Fetus-in-fetu (FIF) is a rare embryological anomaly in which an encysted fetiform mass develops within the infant or adult host body. It mainly occurs intraabdominal. There are embryo-pathogenetic debates over whether it belongs to the spectrum of highly differentiated teratomas or is a parasitic twinning from a monozygotic monochorionic diamniotic pregnancy. The presence of vertebral segments and an encapsulating cyst can reliably distinguish FIF from teratoma. The diagnosis may be initially made by imaging modalities such as computed tomography (CT) and magnetic resonance imaging (MRI), and a confirmatory diagnosis made by histopathology of the excised mass. Our center experienced a case of a male neonate presented after emergency cesarean delivery at 40-week gestation with the suspicion of an intraabdominal mass identified antenatally. Antenatal ultrasonography at 34 weeks gestation suggested the presence of an intraabdominal cystic mass measuring 6.5 cm with a hyperechoic focus. A follow-up MRI performed after the delivery showed a well-defined mass with the cystic formation in the left abdominal region with a centrally located fetiform structure. Vertebral bodies and long limb bones were visualized. The diagnosis of FIF was initially made preoperatively by the characteristic findings of imaging studies. Laparotomy was scheduled on day 6, revealing a large encysted mass with fetiform content. FIF should be considered a possible differential diagnosis of neonatal encysted fetiform mass. Routine antenatal imaging permits more frequent antenatal detection with earlier workup and management.

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

A prenatally diagnosed abdominal mass at 36 weeks and 0 days was further characterised by postnatal ultrasound and MRI to be likely a rare case of fetus in fetu in an otherwise healthy male. Due to close proximity to both the coeliac axis and superior mesenteric artery (SMA), surgical excision was delayed for several months. Interim CT with intravenous contrast performed at 2 months of age demonstrated the SMA travelling through the posterior aspect of the mass. Surgery proceeded at 2 months of age. Intraoperative ultrasound was used to definitively identify both the coeliac axis and SMA in order to facilitate a safe excision. The patient recovered well with an uneventful discharge to home on postoperative day 8. Pathology confirmed the diagnosis of fetus in fetu.

Case Report: The Medical and Surgical Management of an Infant With Extreme Prematurity and Fetus-In-Fetu

Fetus-in-fetu (FIF) is a rare congenital anomaly where a parasitic twin is within the body of a host twin. FIF is reported to occur in 1:500,000 live births. Herein, we report the first case of the medical and surgical treatment of a FIF patient who was born with extreme prematurity at 25-weeks gestation. With the multi-disciplinary coordination of neonatology, surgery, and interventional radiology, the patient was able to achieve a window of medical stability 4 weeks after birth. A decision was made at that time to proceed with an intra-abdominal and perineal resection of the FIF. The FIF was successfully resected and the patient was able to recover from the operation, with eventual discharge from the NICU. In conclusion, extreme prematurity and FIF may be amenable to surgical resection and a multi-disciplinary approach is crucial to achieve the desired outcome.

Fetus-in-Fetu: A Case of Ovarian Involvement and Residual Regrowth in a Teenager

BACKGROUND

Fetus-in-fetu (FIF) is a rare, congenital soft tissue mass typically occurring retroperitoneally in neonates younger than 18 months. We present a 13-year-old girl with an ovarian FIF occurrence and subsequent residual regrowth after resection.

CASE

A 13-year-old girl presented with abdominal pain and was found to have a 19-cm, complex, right adnexal mass. Preoperative tumor markers were normal and risk assessment favored a benign process. She underwent open ovarian cystectomy with pathology showing FIF. Nine months later, she had a recurrence of her ovarian mass and underwent right oophorectomy, with FIF on pathology.

SUMMARY AND CONCLUSION

In patients in whom FIF is discovered within the ovary, consider postoperative surveillance, because of the risk of recurrence or residual disease.

Ovarian Fetiform Teratoma in a 17-Year-Old Adolescent Girl

Fetiform teratoma, also recognized as a homunculus, is a largely uncommon form of mature cystic teratoma. Here, we present the case of a 17-year-old single female who presented to the emergency department complaining of abdominal distension and pain for four months. Abdominal examination revealed a left-sided mass. Magnetic resonance imaging showed a multi-loculated and multi-septated left cystic ovarian mass, suspicious for a teratoma. The patient underwent laparoscopy and a left cystectomy was performed. The final histopathologic diagnosis was consistent with fetiform teratoma. Although extremely rare, ovarian fetiform teratoma should be considered in the differential diagnosis of women presenting with an abdominopelvic mass. It should be discerned from fetus-in-fetu and ectopic pregnancy. Careful clinical presentation, laboratory testing for beta-human chorionic gonadotropin, histopathologic examination, and cytogenetic analysis can greatly aid in pinpointing the diagnosis. Overall, fetiform teratoma carries a favorable prognosis; however, follow-up surveillance is advised to monitor for uncommon occasions of tumor persistence or relapse.

Intra-abdominal fetus in fetu presenting at 31 weeks gestational age

Fetus in fetu (FIF) is a rare anomaly of diamniotic monochorionic twins, in which a malformed fetus resides in its twin's body. This report shows a case with the prenatal diagnosis of FIF at Tu Du hospital. A 23-year-old woman, first-time pregnant, presented at the hospital with an abdominal mass in the fetus at 31 weeks and 4 days of gestation. The ultrasound showed an abnormal mass with the images of calcified features located in the left hypochondriac region and the kidney's upper pole. These images had shapes of skull, femur, spine and became more apparent as the fetus grew. Then, the patient was monitored and delivered at our hospital. The infant was moved to the Children's Hospital 1 and diagnosed with FIF by ultrasound. The surgical resection was performed at 12 days of birth.

First Case Report of Adnexal Fetus in Fetu

BACKGROUND

There is an ambiguous and controversial line between fetiform teratoma and fetus in fetu (FIF) as differential diagnoses of a fetiform mass. Classically, the presence of vertebral column often with a relatively proper arrangement of other organs around the central axis favor the diagnosis of FIF over teratoma.

CASE

Based on previously proposed criteria and the presence of vertebral organization in the radiological and histopathological assessment of the fetiform mass, we present an extremely rare case of adnexal FIF in a 10-year-old girl presenting with acute abdominal pain.

SUMMARY AND CONCLUSION

Whether FIF and fetiform teratoma are one entity or two, clinical discrimination for the choice of treatment seems to be unnecessary and the patient should be clinically followed for the probable malignant potential.

A case report of fetus in fetu with an aorta-like structure visualized by contrast-enhanced CT

Fetus in fetu (FIF) is a rare congenital anomaly resulting from abnormal embyogenesis in monochorionic diamniotic twins and appears as a cystic mass containing fetus-like structures mainly in the retroperitoneum of infants. Although there is a theory that FIF is a highly differentiated teratoma, it is commonly distinguished from teratoma as a mass containing a vertebral axis with appropriate arrangement of limbs or other organs around this axis. Here we present a case of FIF with aorta-like structure visualized by contrast-enhanced computed tomography. A 5-day-old girl was pointed out a cystic mass in the abdomen by ultrasound examination. Abdominal contrast-enhanced computed tomography revealed a retroperitoneal cystic mass with spine- and limb-like bone structures and blood vessel-like elongated structures and it was confirmed as FIF by surgery. The presence of major vascular structures along the skeletal axis is clearly different from teratoma and suggests that it occurred as an embryo and underwent some stage of development. Our findings strongly support the monozygotic twin theory.

Prenatal diagnosis of a "living" oropharyngeal fetus in fetu: a case report

BACKGROUD

Fetus in fetu (FIF) is a rare malformation in which a parasitic twin within its more mature twin. Most of the FIF locate in the retroperitoneum and are acardiac and anencephalic.

CASE PRESENTATION

Here, we describe a unique case of oropharyngeal fetus in fetu with a rudimentary two-chambered heart detected by prenatal ultrasonography. The parents terminated this pregnancy after counseling. Macroscopic examination found a solid mass between the oral and fetal chest, with a rudimentary two-chambered heart at the lowest part of the mass. Microscopic findings showed amniotic membrane, skin, cartilage, gastrointestinal and neural tissue.

CONCLUSIONS

Prenatal ultrasound can identify rudimentary organs suspecting FIF from early pregnancy. Detection of fetal heart beat facilitates differential diagnosis with teratomas, providing essential information for parental consulting and management.

Human germ cell tumours from a developmental perspective

Human germ cell tumours (GCTs) are derived from stem cells of the early embryo and the germ line. They occur in the gonads (ovaries and testes) and also in extragonadal sites, where migrating primordial germ cells are located during embryogenesis. This group of heterogeneous neoplasms is unique in that their developmental potential is in effect determined by the latent potency state of their cells of origin, which are reprogrammed to omnipotent, totipotent or pluripotent stem cells. Seven GCT types, defined according to their developmental potential, have been identified, each with distinct epidemiological and (epi)genomic features. Heritable predisposition factors affecting the cells of origin and their niches likely explain bilateral, multiple and familial occurrences of the different types of GCTs. Unlike most other tumour types, GCTs are rarely caused by somatic driver mutations, but arise through failure to control the latent developmental potential of their cells of origin, resulting in their reprogramming. Consistent with their non-mutational origin, even the malignant tumours of the group are characterized by wild-type TP53 and high sensitivity for DNA damage. However, tumour progression and the rare occurrence of treatment resistance are driven by embryonic epigenetic state, specific (sub)chromosomal imbalances and somatic mutations. Thus, recent progress in understanding GCT biology supports a comprehensive developmental pathogenetic model for the origin of all GCTs, and provides new biomarkers, as well as potential targets for treatment of resistant disease.

Fetus in fetu in an adult woman

Fetus in fetu (FIF) is an extremely rare condition in which malformed fetus is found most commonly in the retroperitoneum of living twin. It occurs in about 1 in 500 000 live births and less than 200 cases have been reported in medical literature. We report FIF in a 17-year-old woman unlike other cases which were usually detected in early age and in male gender. This is the eighth case of adult FIF and the first case of FIF in adult woman worldwide. Preoperative diagnosis of FIF on CT was made and planned for exploratory laparotomy. The excised malformed fetus in a sac was proven as FIF on the basis of histopathological examination. In view to avoid such late presentation, early detection of FIF with radiological imaging in clinically suspected case is recommended. Surgical excision is the ideal treatment even teratoma is the differential diagnosis.

The entrapped twin: a case of fetus-in-fetu

Fetus-in-fetu (FIF) is a rare entity in which malformed parasitic twin grows inside the body of its twin. It is most commonly presented with mass in the abdomen. We present a case of a 15-year-old boy who presented with abdominal mass since infancy. Radiological investigations are suggestive of FIF. Intraoperatively, malformed fetus in a sac was found and excised. Postoperatively the patient recovers well and was put on follow-up.