Fetus in fetu: molecular analysis of a fetiform mass

Intra-abdominal retroperitoneal fetus in fetu: A case report

Fetus in fetu (FIF) is a rare abnormality where a vertebrate parasitic fetus develops inside the body of another normally developing fetus. It is distinct from teratomas, tumors composed of cells from multiple germ layers and have malignant potential. Symptoms of FIF arise from the mass effect, causing abdominal distension, feeding difficulties, and pressure effects on organs. FIF is commonly found in the retroperitoneal region but can also occur in other locations. It often includes certain organs such as the vertebral column, limbs, central nervous system, gastrointestinal tract, vessels, and genitourinary tract. Early diagnosis of FIF by ultrasound, computed tomography, and magnetic resonance imaging can improve patient outcomes. Surgical resection is the primary treatment approach, aiming to alleviate symptoms, and molecular analysis helps differentiate FIF from malignant teratomas. Regular follow-up is necessary due to the potential recurrence of teratomas.

Neonatal Malignant Disorders: Germ Cell Tumors

Germ cell tumors (GCTs) comprise a wide spectrum of benign and malignant tumors. Neonatal GCTs are predominantly teratomas (mature or immature), which are typically cured with surgery alone. Relapses are infrequent even in the setting of microscopic residual disease; therefore, negative surgical margins at the cost of significant morbidity are not recommended. In neonates with metastatic malignant disease or malignant disease for which upfront surgical resection is not feasible without significant morbidity, an initial biopsy followed by neoadjuvant chemotherapy and delayed surgical resection is recommended. Carboplatin-based regimens should be considered when chemotherapy is indicated.

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 of cephalomelia discovered in a baby born in Niger

INTRODUCTION

Subcutaneous tumors with extra limbs are very rare, and they are considered either as fetus in fetu or fetiform teratoma.

CASE REPORT

We report here the case of a 6-day-old presenting a mass extending at the level of the occipital bone. This mass is developed in the extracranial region and contains two forelimbs including hands with digits. CT shows that the squamous part of the occipital bone is involved with several defects through which a part of the cerebellum herniates. The boy was operated on and the tumor was removed. The herniated region of the cerebellum has also been removed. After surgery, the boy develops normally.

CONCLUSION

This type of tumor is extremely rare and is only the second case that has been reported at this exact location. This could be the so-called céphalomélie described by Isidore Geoffroy Saint-Hilaire in a duck in his famous Treatise of Teratology (1836). The cause of this malformation is still a matter for debate.

Fetus in Fetu in the Scrotal Sac: Case Report and Literature Review

Fetus in fetu (FIF) is a rare congenital anomaly. The most common site at which FIF occurs is the retroperitoneum. The mechanisms underlying the development of FIF have not been fully elucidated. The monozygotic twin theory postulates that FIF results from the unequal division of the totipotent cells of the blastocyst. However, the monozygotic twin theory does not explain all cases of FIF.Herein, we describe the clinical characteristics of a 20-day-old infant with scrotal sac swelling. Ultrasonography and computed tomography revealed the presence of a mass consistent with a FIF rather than a teratoma. Surgical removal and a subsequent pathological evaluation demonstrated that the anencephalic fetus exhibited limb buds adjacent to a palpable vertebral column, supporting the diagnosis of FIF. The infant had an uneventful recovery and was discharged on the fifth postoperative day. In the present report, the pathogenesis, presentation, diagnosis, and management of FIF, as well as new concepts emerging in this area of research, are discussed.Although the majority of cases of FIF may be diagnosed preoperatively, FIF should be distinguished from teratoma because the latter has substantial malignant potential. The recommended treatment for FIF is complete resection. To confirm the diagnosis of FIF, pathological examination, karyotyping, serologic marker assessment, and DNA restriction site mapping should be performed after removing the mass. Although FIF is thought to be a benign disorder, follow-up is necessary as a precaution against malignant recurrence, which has been described once.

Fetus in Fetu

Fetus in fetu is a congenital abnormality in which a nonviable, parasitic fetus grows within its twin. It is a rare cause of retroperitoneal abdominal mass in infants and children. The authors report a recent case of a six-month-old girl who presented with unexplained abdominal distention. A sonogram and a magnetic resonance imaging examination showed a multiloculated, complex cystic mass with calcified and soft tissue components. A definitive diagnosis and discrimination from a teratoma was difficult to make because of the absence of a distinctive criterion, the presence of a vertebral column. Pathologic examination showed a complex mass consisting of well-formed bowel and upper respiratory tract segments as well as mature neuroglial tissue, skeletal muscle tissue fibers, and bone tissue that contained bone marrow, supporting the diagnosis of fetus in fetu. Therefore, the nonvisualization of a vertebral column on imaging should not exclude fetus in fetu from the differential diagnosis.

Fetus in fetu: two case reports and review of literature

Fetus in fetu is a rare disorder. Its embryopathogensis and differentiation from teratoma has not been well established. It is a parasitic twin of a diamniotic monozygotic twin. Here we report, two cases of fetus in fetu with review of literature. In case report 1, a 2-year-old boy was referred for asymptomatic lump in abdomen since birth. X-ray showed the mass in the abdomen with some calcification and fluid inside. CT scan reported a heterogenous mass in the retroperitoneum with bony malformation. CT showed presence of three vertebrae in it. After surgically excising the mass and opening the sac it showed presence of trunk and two limbs with one of the limbs having a nail. Histopathology showed presence of GI tract. In case report 2, 4 month female was found to have lump in the abdomen by housemaid while bathing. X-ray showed a soft tissue shadow while ultrasonography revealed cystic mass arising from right kidney. CT suggested cystic mass with calcification not arising from kidney. During exploration whole mass was excised and there was frank fetus inside it. Histopathology confirmed presence of four vertebral bodies with germ layers. Although fetus in fetu is rare condition, correct diagnosis using imaging can be made before surgery. Complete excision is curative.

Fetus-in-fetu in the cranium of a 4-month-old boy: histopathology and short tandem repeat polymorphism-based genotyping. Case report

Fetus-in-fetu is a very rare condition in which one fetus is contained within another. About 100 cases have been reported, and in most of these the fetus was located in the retroperitoneum. The authors describe an extremely rare case of an intracranial fetus-in-fetu in an extraaxial location. This is the eighth intracranial fetus-in-fetu to be reported, the first intracranial extraaxial case, and involves the oldest documented patient with this condition. Histopathological analysis of the mass revealed a degenerated amnionic membranelike tissue, well-differentiated extremities (including fingerlike structures), skin, matured lungs, well-formed intestines, cerebellar and cerebral tissue, and a notochord with ganglion cells. DNA analysis using short tandem repeat polymorphisms confirmed that the fetus-in-fetu mass and the host infant had heterozygous alleles and were of identical sex and genotype.

Intracecal fetiform teratoma

Fetiform teratoma is a rare form of mature cystic teratoma that is highly developed and organized, resembling a fetus-like structure. These are rare entities that have been typically described in women of reproductive age and most often present as ovarian masses. Only two cases of a fetiform teratoma have been reported in a male. Although teratomas are a common benign entity, only five prior cases of teratoma involving the cecum have been described. We present an atypical case of an intracecal fetiform teratoma occurring in a 2(1/2)-year-old Chinese boy.

Fetus in fetu--from prenatal ultrasound and MRI diagnosis to postnatal confirmation

We report a case of fetus in fetu presented as a complex intra-abdominal heterogeneous cystic lesion during ultrasound examination of the fetus at 25 weeks of gestation. Progressive growth of this mass was noted in the prenatal period. Fetal magnetic resonance imaging provided additional information to aid in the prenatal diagnosis. This allows proper counselling for the parents and helps to plan the postnatal management. Surgical excision was carried out in the early neonatal period and the diagnosis of fetus in fetu was confirmed.

Fetiform teratoma (homunculus)

Fetiform teratoma (homunculus) is a term that has been given to a rare form of ovarian teratoma that resembles a malformed fetus. There are very few reported cases of this entity in the English language literature. In this report, we document a case of fetiform teratoma in a 23-year-old woman, gravida 0, who initially presented with a chief complaint of dyspareunia. The clinical and pathologic aspects of this rare entity are presented here, with a review of the English literature. Differentiating fetiform teratoma from the more highly developed fetus-in-fetu and ectopic pregnancy is also discussed.

Origin and mechanisms of formation of fetus-in-fetu: two cases with genotype and methylation analyses

Fetus-in-fetu (FIF) is a condition in which a host infant has a fetus-like mass(es) within its body. We describe here results of molecular genetic analysis in two cases of FIF. In FIF-1, a male host had two retroperitoneal fetiform masses each with a vertebral column, and in FIF-2, a fetiform mass with vertebral column was present in the cranial cavity of a male host. Genotyping of each case using microsatellite markers showed that the host infant and its fetus(es) inherited one copy each of parental alleles and shared identical genotypes. These findings were confirmed by single nucleotide polymorphism (SNP) analysis using Affymetrix GeneChip Human Mapping 50K Array, and supported a monozygotic twin theory of FIF. Analysis of the methylation status was done in both cases at the differentially methylated region (DMR) within the human IGF2-H19 locus after bisulfite treatment, methylation-specific PCR, and cloning of PCR products. Normally, only the paternal allele is methylated and the maternal allele unmethylated in DMR. However, in FIF-1, 7 (46.7%) of 15 clones from a fetiform mass and 6 (66.7%) of 9 clones from the other mass showed an unmethylated paternal allele, while the methylation status of a host infant and its fetiform mass in FIF-2 was the same in all clones examined with normal patterns. These data suggest that in FIF-1, two isolated blastocysts originated from one zygote, one of the two was implanted into (or included by) the other blastocyst during the process of methylation, and such abnormal implantation may have occurred in FIF-2 after the establishment of methylation. This is the first case of FIF showing different methylation patterns between a host infant and fetiform mass.

Perinatal (fetal and neonatal) germ cell tumors

BACKGROUND/PURPOSE

Germ cell tumors are relatively common in the fetus and neonate and are the leading neoplasms in some perinatal reviews. The purpose of this study is to focus on the fetus and neonate in an attempt to determine the various ways germ cell tumors differ clinically and morphologically from those occurring in the older child and adult and to show that certain types of tumors have a better prognosis than others.

METHODS

The author conducted a retrospective review of perinatal teratomas and other germ cell tumors reported in the literature and of patients treated and followed up at Children's Hospital San Diego and Children's Hospital Los Angeles. Only fetuses and infants less than 2 months of age with adequate clinical and pathologic data were accepted for review.

RESULTS

Five hundred thirty-four fetuses and neonates presented with teratomas diagnosed prenatally (n = 226) and at birth (n = 309). The most common initial finding was a mass, noted either by antenatal sonography or by physical examination during the neonatal period, with signs and symptoms referable to the site of origin. Overall polyhydramnios was next followed by respiratory distress and stillbirth. The number of mature and immature teratomas was approximately the same. The incidence of teratoma with yolk sac tumor either at presentation or at recurrence was 5.8%, and the survival rate was 39%. Sacrococcygeal teratomas had the highest incidence of yolk sac tumor at 10%. Recurrent disease in the form of either teratoma or yolk sac tumor developed in 5% of patients. All individuals with teratomas who survived received surgical resection.

CONCLUSIONS

Some germ cell tumors of the fetus and neonate have a better prognosis than others. Neonates with gastric teratomas have the best survival rates, and those with intracranial germ cell tumors the worst. Fetuses with teratomas detected antenatally have 3 times the mortality rate compared with postnatally diagnosed neonates. Although perinatal teratomas have a relatively low recurrence rate of 5%, close follow-up with imaging studies and serum alpha-fetoprotein determinations is is strongly recommended. Surgical resection alone may be adequate therapy for teratomas with nonmetastatic, microscopic foci of yolk sac tumor. In the nonteratoma group, patients with pure yolk sac tumor and gonadoblastoma have a much better outcome than those with choriocarcinoma, which has a very low survival of rate of 12%. Currently, the use of platinum-based combination chemotherapy has significantly improved the survival rate of infants with advanced malignant germ cell tumor disease.

Mature ovarian cystic teratoma with a highly differentiated homunculus: A case report

BACKGROUND

Mature ovarian cystic teratomas, which are commonly observed benign ovarian tumors, consist of ectodermal, mesodermal, and endodermal components that are generally disorganized. In this report, we document a case in which the solid portion of an ovarian teratoma demonstrated considerable differentiation, forming a doll-like structure.

CASE

A 25-year-old virginal Japanese woman underwent surgery for an ovarian tumor that was diagnosed as a mature teratoma. A solid mass within the tumor was found to have a head, trunk, and extremities. Consequently, this mass was diagnosed as a mature fetiform teratoma (homunculus). Brain, eye, spinal nerve, ear, teeth, thyroid gland, bone, bone marrow, gut, trachea, blood vessels, and phallic cavernous tissue were confirmed microscopically. Distinctive features were the clear anterior-posterior, ventral-dorsal, and left-right axes, with a spatially well-organized arrangement of the organs. An eye was located on the front of the head, a spinal nerve lay dorsal to the spinal bones, the thyroid gland was anterior to the trachea, and the gut was deep inside the trunk.

CONCLUSIONS

These findings indicate that the information necessary for organization of the body plan may be conserved and transmitted, even with parthenogenesis. Mature cystic teratomas of the ovary are mostly benign and do not always attract detailed attention. However, precise analyses of such tumors may significantly enhance our understanding of both parthenogenetic and normal human development.

Fetus-in-fetu form of monozygotic twinning with retroperitoneal teratoma

One of the commonest defects of blastogenesis is monozygotic twinning resulting in separate or conjoint twins, the latter including a category of internal, "endoparasitic," or fetus-in-fetu twins. We report the third known instance of endoparasitic twinning associated with a benign teratoma at age 1. The host, twin, and teratoma were monozygotic by DNA analysis.

Ultrasound prenatal diagnosis of fetus in fetu

A case of fetus in fetu was diagnosed prenatally using ultrasound. The differential diagnosis between a fetus in fetu and a highly differentiated teratoma is discussed. The importance of prenatal diagnosis of fetus in fetu and the effect on subsequent management are described.

Oral mature teratoma containing epididymal tissue in a female neonate

We describe a female neonate with an oral teratoma showing bone, teeth, and epidermis, but also epididymal (male) tissue. PCR amplification of Y-chromosomal DNA clearly showed male DNA from paraffin-embedded tumour tissue. The girl had a normal female karyotype without abnormalities of the genital organs. There are at least three hypotheses for the origin of teratomas: parthenogenesis, incomplete twinning, and totipotent somatic-cell origin. This case supports the hypothesis of an included dizygotic twin, and might contribute to the elucidation of the pathogenesis of extragonadal teratomas.

Fetus in fetu: a case report and literature review

Fetus in fetu is a rare condition in which a fetiform calcified mass often is present in the abdomen of its host, a newborn or an infant. We report on a case of a 19-month-old girl whose plain abdominal radiograph, ultrasonography, and computed tomography scan revealed a mass in which the contents favor a fetus in fetu rather than a teratoma. The noncalcified vertebral column invisible on the radiographs was identified by the pathologist; therefore, the nonvisualization of the vertebral axis on radiography or on computed tomography scan does not exclude the diagnosis of fetus in fetu.

Fetus-in-fetu presenting as cystic meconium peritonitis: diagnosis, pathology, and surgical management

Fetus-in-fetu (FIF), a rare congenital anomaly, is a fetus incorporating the well-differentiated tissue of its twin. The authors describe a newborn who presented with massive abdominal distension and severe respiratory distress. Abdominal x-rays showed multiple calcifications. The diagnosis of meconium pseudocyst was made. At emergency laparotomy an irregular fetiform mass was found in the retroperitoneum lying within a fluid-filled amniotic sac. It contained a vertebral column, 10 limblike structures, and cranial and caudal ends, supporting the diagnosis of fetus-in-fetu. This case highlights several important points. FIF often is overlooked in the differential diagnosis of a newborn abdominal mass and, as in this case, may be confused with meconuim pseudocyst. FIF should be differentiated from a teratoma because of the latter's malignant potential. Because this diagnosis is not made until pathological analysis, all parts of the mass should be removed to prevent malignant recurrence.

Fetus-in-fetu: a case report with molecular analysis

This is the report of a case of fetus-in-fetu diagnosed in a 3-month-old boy and found to be located in the upper retroperitoneum. The entity was distinguished from teratoma by the presence of vertebral axis with limb buds. It corresponded to a diamniotic, monochorionic, monozygotic twin. Complete excision of the mass was performed. Radiological, histopathologic, and DNA fingerprinting studies performed on fetus-in-fetu specimen showed that the fetus was a monozygotic twin.

Fetus-in-fetu: a case report and review of the literature

A unique case of intraperitoneal fetus-in-fetu attached to an ovary is presented. An asymptomatic newborn girl was found to have a mobile cystic mass in right side of her abdomen. Radiological investigations showed fetus-in-fetu. During laparotomy, an intraperitoneal fetus-in-fetu was found attached to right ovary and vascular pedicle to ovarian vessels. Only 79 cases of fetus-in-fetu have been reported, and this is the first such case attached to an ovary.

Unusual presentation of heteropagus attached to the thorax

The endoparasitic twin is the most common form of asymmetric fetal duplication (heteropagus). A 2-month-old girl who had a parasitic right lower limb with axial skeleton, vertebral column, uterus, fallopian tube, ovary, and bladder implanted in the sternum region is described as another example of exoparasitic twin, the uncommon form of heteropagus. Unusually, dextrocardia was found in the autosite. This report emphasizes the even progression between the endoparasitic and exoparasitic forms of heteropagus.