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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.

ABSTRACT Fetiform teratoma, another name for homunculus, is a rare form of mature teratoma that is highly differentiated and has parts that resemble a malformed fetus. We reported a case of ovarian Fetiform teratoma in a 38 years old nulliparous woman presented with right side abdominal distention of 10 years duration. An ultrasound revealed a heterogeneous pelvic cystic mass that ranged in appearance from fully hyperechoic to fully hypoechoic, suggesting mature cystic teratoma. The patient underwent laparotomy. Histopathology of Cystectomy specimen was found to be compatible with Fetiform teratoma. It is important to distinguish this highly differentiated benign neoplasm with potential somatic malignant transformation from Fetus in fetu and ectopic pregnancy. To establish the diagnosis, a thorough clinicopathologic examination, laboratory tests for pregnancy and relevant cytogenetic tests for Zygosity should be performed.

Fetus in fetu is a rare congenital anomaly in which a malformed parasitic twin is found within the body of a living child or adult. In this case report, a 1-day-old child presented with a large firm abdominal mass on the left side of the upper abdomen. Imaging studies misdiagnosed the mass as an intraperitoneal benign dermoid cyst displacing the bowel loops and internal viscera. A surgical resection was performed on 21 days of life, and pathology confirmed eight fetuses inside the cyst.

Fetus in fetu is a rare congenital anomaly in which a malformed parasitic twin is found within the body of a living child or adult. In this case report, a 1-day-old child presented with a large firm abdominal mass on the left side of the upper abdomen. Imaging studies misdiagnosed the mass as an intraperitoneal benign dermoid cyst displacing the bowel loops and internal viscera. A surgical resection was performed on 21 days of life, and pathology confirmed eight fetuses inside the cyst. [ABSTRACT FROM AUTHOR]

Background: Fetus in fetu (FIF) is an exceedingly rare congenital anomaly characterized by the presence of a partially developed fetus within the body of its twin. It is a rare entity with fewer than 200 cases documented worldwide. Typically presenting as an abdominal mass in early childhood, this condition remains a diagnostic challenge due to its infrequency and varied clinical manifestations. Case presentation: We present the case of a 1-year-old female child referred to the pediatric surgery department due to an abdominal mass detected by her parents. Physical examination revealed a firm, ill-defined mass in the right upper abdomen. Ultrasonography delineated a heterogeneous, calcified mass in the right upper quadrant. Laboratory investigations (complete blood count, viral markers), including tumor markers (AFP, beta-hCG), were within normal limits.A midline laparotomy was performed, and intraoperative findings revealed a well-encapsulated mass adherent to the retroperitoneum, adjacent to the liver. Careful dissection was carried out to preserve vital structures, and the mass was successfully removed without rupture. Histopathological examination confirmed the diagnosis of fetus in fetu, displaying a spectrum of tissues reminiscent of embryonic development, including skin, adnexal structures, brain tissue, mature cartilage, adipose tissue, bone marrow elements, and a partially developed vertebral column. After the surgical resection, the patient experienced an uneventful postoperative recovery. At one year of follow up the patient has shown no signs of recurrence. Conclusion: FIF is characterized by diagnostic challenges, often requiring postoperative histological confirmation. Histopathological examination confirmed the presence of FIF. Surgical excision, is crucial for favorable outcomes, especially in preventing potential complications. Comprehensive histopathological evaluation remains imperative for accurate diagnosis.

Fetus in fetu is a rare congenital anomaly with fewer than 200 cases reported worldwide. It is a part of spectrum of anomalous embryogenesis. We report a case of an 18-month old boy with abdominal distension. Ultrasonography, X-ray, and computed tomography (CT) scan revealed a retroperitoneal mass suggestive of fetus in fetu. with evidence of organogenesis and a vertebral column, which differentiates it from an organized teratoma. The mass was resected in toto.

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.

Key Clinical Message: Fetus in fetu (FIF) is a rare congenital anomaly that originates from various sites of the host twin's body. The clinical manifestations of FIF are diverse and the location and size of FIF indicate the degree of threat, which may directly affect the prognosis. A 33‐year‐old woman presented at the hospital with an abdominal mass in her fetus. Prenatal ultrasound observed that mass included soft tissue, bone‐like structures, and fluid. Immature cartilage, nerve tissue, muscle tissue, and glands in the parasitic fetus without signs of neoplastic lesions were reported by histological examination. CNV (copy number variation) and WES (whole exome sequencing) did not detect any abnormal mutations. FIF can continue to grow with gestational age or host infant growth. So complete resection is essential for improving the outcome of the host twin. It is also important that long‐term follow‐up is recommended to monitor any residual or recurrent cysts or malignancies. [ABSTRACT FROM AUTHOR]

Fetus in fetu was first identified in the early 19th century by Meckel. It is a rare congenital anomaly which occurs from anomalous embryogenesis in which a malformed parasitic twin is found within the body of the normally developed host. In most cases, the parasitic twin is anencephalic and usually contains a vertebral column and budding limbs. The upper limbs are less developed than lower limbs, and are usually located in the abdomen of the autosite. Diagnosis is often made preoperatively with ultrasonography, plain radiography, computed tomography, or magnetic resonance imaging. Histopathological findings confirm the diagnosis and the recommended treatment is complete surgical excision of mass. We report a case of 15-month-old baby boy of Nepalese origin referred to our hospital with mass in abdomen diagnosed during neonatal period. [ABSTRACT FROM AUTHOR]

Fetus in fetu is a rare congenital anomaly with fewer than 200 cases reported worldwide. It is a part of spectrum of anomalous embryogenesis. We report a case of an 18-month old boy with abdominal distension. Ultrasonography, X-ray, and computed tomography (CT) scan revealed a retroperitoneal mass suggestive of fetus in fetu. with evidence of organogenesis and a vertebral column, which differentiates it from an organized teratoma. The mass was resected in toto. [ABSTRACT FROM AUTHOR]

Fetus in fetu (FIF) is a rare congenital disease caused by the abnormal development of monochorionic diamniotic twins that appears as a cystic mass containing fetus-like structures mainly in the retroperitoneum of infants. The clinical manifestations of fetus in fetu vary, but they mostly present at infancy, hence, it should be differentiated from a teratoma. Here, we report a case of an infant with fetus in fetu in the retroperitoneum. Enhanced computed tomography scans and three-dimensional images showed a huge mixed-density mass on the left side of the abdominopelvic cavity with patchy distribution of fat, intact bones, and soft tissue. The child underwent fetus in fetu resection under general anaesthesia. Histopathology confirmed that the mass contained skin, muscle, intestinal mucosa, bones and cartilage, nerves, muscles, fat, and bone marrow tissue.

Abstract Background The fetu in fetu (FIF) is an extremely rare congenital condition characterized by a 2nd fetus that grows into the body of the healthy twin. Its thoracic location is more exceptional. Case presentation We report a case of intrathoracic mass in a 5-month-old female infant, diagnosed after an assessment for respiratory distress. She underwent an emergency left thoracotomy which allowed for the removal of a large thoraco-mediastinal mass inside a membranous sac containing a clear liquid mixed with vernix caseosa. The mass was completely covered with normal skin, three lobes similar to rudimentary outline of the head and limb. It was attached to a single large vascular pedicle. The pathological examination concluded that there was a high possibility of FIF. The postoperative follow-up was uncomplicated, and the child is still in good clinical condition after the 5-month follow-up. Conclusion The assessment of the respiratory distress in an infant with a mass centered by an axial skeleton on the chest x-ray and thoracic CT scan may suggest a diagnosis of intrathoracic FIF.

Abstract Background Fetus in fetu is a rare condition in which a malformed fetus is found in the body of a living twin. The retroperitoneum is the most common location of this condition. However, the sacrococcygeal region is a rare site of the disease. The presence of vertebral bodies and limbs differentiates FIF from teratoma. Imaging modalities are important for diagnosing FIF. Case presentation A 12-months old boy was hospitalized because of a mass in the sacrococcygeal region. CT showed a large, complex mass with bony structure resembling sacrococcygeal bone, hip bone and the femur in the sacrococcygeal region of the boy. The blood supply of the mass was from the aorta of the host. MRI revealed the mass was connected with the dilated sacral canal of the host, which resulted in tethered cord. A preoperative diagnosis of FIF was made and surgery was performed to remove the mass. Surgical removal and subsequent pathological examination revealed the anencephalic fetus had limb buds and a sacrum but no axial skeleton, which supported the diagnosis of FIF. Conclusions CT and MRI played important roles in diagnosing FIF based on the location of the lesion.

Teratoma is a congenital neoplasm deriving from one or more embryonic layers. Fetiform teratoma is a highly differentiated rare type of teratoma. The authors present a 1-day-old neonate for a lumbar region mass, grossly appearing like an extremity. CT scan was performed showing a highly organized extremity skeleton in the lumbar region consisting of flat, long and short bones. Fetiform teratoma should be differentiated from a fetus in fetu, as the former lacks axial skeleton while it is the main feature of the latter, respectively. Both have different prognostic implications, and surgical excision is the treatment of choice.

Fetus in fetu (FIF) is a rare congenital anomaly. Anomalies of inferior vena cava (IVC) in the host are rare and not reported in the literature. In this case report, the surgical management and the findings of a rare vascular anomaly of IVC in a 10-month-old male child with FIF are discussed. This case highlights the importance of antenatal ultrasonogram in the detection of FIF and to diligently look for structural anomalies of IVC in the host in such cases.

Background: Fetus in fetu (FIF) is a rare congenital anomaly in which a parasitic fetus is trapped inside the body of its twin. The incidence is 1 in 500,000 births. Initially, considered as a mature teratoma, it was later identified as a separate entity due to the presence of an axial skeleton and organized limbs. Clinical Description: A 48-day-old girl presented with an antenatally detected calcified intra-abdominal mass. She had a palpable retroperitoneal mass measuring 6 cm × 4 cm at the left lumbar area. Sonology showed a heteroechoic cystic mass in the left lumbar region. Serum markers were normal except for a slightly elevated serum lactate dehydrogenase. Contrast-enhanced computerized tomography of the abdomen showed a well-defined cystic lesion measuring 7.6 cm × 6.5 cm × 5.9 cm with enhancing septae, multiple calcific foci, teeth, and bones in the left suprarenal region displacing the left kidney. Management: Laparotomy showed a cystic appearing mass with solid components within. Cystic structure was the amniotic covering and solid component turned out to be the FIF with a face, limbs, and umbilical cord. No adjacent infiltration was seen. Pathology confirmed the finding of FIF with an identifiable vertebral column, umbilical cord, pelvis and lower limb bones, skin, and retinal and brain tissue. The infant has been under follow-up for a year and is thriving. Conclusion: FIF is a rare condition of infancy which can be diagnosed preoperatively by radiological examination, treated by complete excision, and confirmed by gross and histopathology. Differentiation of FIF from teratoma is mandatory as the latter can be malignant.

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.

Antecedentes: Fetus in fetu (FIF) es una rara anomalía congénita de gemelos monocigotos asimétricos, donde el gemelo parásito se desarrolla anormalmente dentro del cuerpo del gemelo huésped. Actualmente hay menos de 200 casos reportados a nivel mundial siendo este el segundo caso en Honduras. Caso clínico: Se reporta el caso de un paciente masculino, recién nacido a término en la sala de maternidad del Hospital San Felipe, quien a su nacimiento se observó distensión abdominal, hernia umbilical, hernia inguino-escrotal izquierda y tumoración en el hipocondrio izquierdo por lo que se decide realizar una radiografía anteroposterior toracoabdominal revelado un tumor en la región izquierda del abdomen con presencia de calcificaciones. Se refiriere al Hospital Escuela Universitario donde se le efectuó un ultrasonido abdominal total con reporte de masa heterogénea de 5 cm3 de volumen con componente cálcico en su interior, que tuvo que ser correlacionada con tomografía axial computarizada con reconstrucción 3D dando como resultado masa heterogenia con huesos axiales y apendiculares en su interior compatible con FIF. Se realizó intervención quirúrgica con resección de tumoración retroperitoneal y sus anexos sin secuelas ni complicaciones por lo cual se da alta médica. Conclusión: Aunque el FIF es una enfermedad muy rara, el tratamiento de elección será la resección de la masa y su pronóstico es favorable cuando la masa se ubica en el área retroperitoneal. Se puede observar que la tomografía tridimensional es una técnica de imagen útil para la diferenciación entre un FIF y un teratoma en el diagnóstico preoperatorio.

Abstract Background Fetus in fetu is a rare congenital anomaly. The exact etiology is unclear; one of the mostly accepted theories is the occurrence of an embryological insult occurring in a diamniotic monochorionic twin leading to asymmetrical division of the blastocyst mass. Commonly, they present in the infancy with clinical picture related to their mass effect. About 80% of cases are in the abdomen retroperitoneally. Case presentation We present two cases of this rare condition. The first case was for a 10-year-old girl that presented with anemia and abdominal mass, while the second case was for a 4-month-old boy that was diagnosed antenatally by ultrasound. Both cases had vertebrae, recognizable fetal organs, and skin coverage. Both had a distinct sac. The second case had a vascular connection with the host arising from the superior mesenteric artery. Both cases were intra-abdominal and showed normal levels of alpha-fetoprotein. Histopathological examination revealed elements from the three germ layers without any evidence of immature cells ruling out teratoma as a differential diagnosis. Conclusions Owing to its rarity, fetus in fetu requires a high degree of suspicion and meticulous surgical techniques to avoid either injury of the adjacent vital structures or bleeding from the main blood supply connection to the host. It should be differentiated from mature teratoma.

Background: The fetu in fetu (FIF) is an extremely rare congenital condition characterized by a 2nd fetus that grows into the body of the healthy twin. Its thoracic location is more exceptional. Case presentation: We report a case of intrathoracic mass in a 5-month-old female infant, diagnosed after an assessment for respiratory distress. She underwent an emergency left thoracotomy which allowed for the removal of a large thoraco-mediastinal mass inside a membranous sac containing a clear liquid mixed with vernix caseosa. The mass was completely covered with normal skin, three lobes similar to rudimentary outline of the head and limb. It was attached to a single large vascular pedicle. The pathological examination concluded that there was a high possibility of FIF. The postoperative follow-up was uncomplicated, and the child is still in good clinical condition after the 5-month follow-up. Conclusion: The assessment of the respiratory distress in an infant with a mass centered by an axial skeleton on the chest x-ray and thoracic CT scan may suggest a diagnosis of intrathoracic FIF. [ABSTRACT FROM AUTHOR]

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.

Introducción. Fetus in fetu es una rara entidad congénita en la cual se presenta un gemelo monocigótico que en la mayoría de los casos está incorporado en el abdomen del hermano. La presentación más frecuente es una masa retroperitoneal. La diferenciación diagnóstica entre fetus in fetu y teratoma es discutida. El objetivo de este trabajo es describir el caso de dos pacientes con fetus in fetu, mediante una revisión reducida de la literatura en sus hipótesis etiológicas y métodos diagnósticos. Reporte de casos. Se presentan 2 casos, el primer caso es un lactante menor con distensión abdominal persistente, en quien se palpó masa abdominal. El segundo caso es un recién nacido con diagnóstico prenatal de masa abdominal. Ambos casos presentan imágenes radiológicas que evidencian masa abdominal compatible con fetus in fetu, razón por la cual posteriormente fueron intervenidos quirúrgicamente para resección de la masa. Discusión. Es importante tener presente esta patología como diagnóstico diferencial de masa abdominal en los pacientes infantes, ya que el poder diferenciarlo de un teratoma maduro nos indicaría que se trata de una alteración del desarrollo embriológico y no de una patología tumoral. Para esto, son necesarios métodos imagenológicos y en algunos casos pruebas cromosómicas o histopatológicas, con el fin de esclarecer el diagnóstico del fetus in fetu. Conclusión. El fetus in fetu es una patología rara con pocos casos diagnosticados prenatalmente, la cual se diagnostica principalmente en la infancia. Las imágenes radiológicas y en algunos casos las pruebas cromosómicas o histopatológicas, son de gran importancia para el diagnóstico definitivo. Cómo citar. Lubinus F, Zuñiga-Hadechni E, López L, Rueda-Hernández, CA. Fetus in fetu, presentación de dos casos: diagnóstico diferencial y revisión de la literatura. MedUNAB. 2020;23(3):464-470. doi: doi.org/10.29375/01237047.3685 Introduction. Fetus in fetu is a rare congenital condition that has been defined as the presence of one monozygotic twin, in most cases, in the sibling’s abdomen. It is most frequently present as a retroperitoneal mass. The diagnostic difference between fetus in fetu and teratoma is discussed. This work’s objective is to describe the case of two patients with fetus in fetu through a reduced literature review in terms of etiologic hypotheses and diagnostic methods. Case Reports. Two cases are presented. The first case is that of an infant with persistent abdominal distension, in whom an abdominal mass was found by palpating. The second case is that of a newborn baby with a prenatal abdominal mass diagnosis. Both cases present X-ray images that demonstrate an abdominal mass compatible with fetus in fetu, reason why the patients were subsequently surgically intervened to remove the mass. Discussion. It is important to keep this pathology in mind as a differential diagnosis of abdominal masses in infant patients, since being able to differentiate it from a mature teratoma would indicate that the mass is an embryonic development alteration, not a tumor pathology. Imaging methods and, in some cases, chromosome or histopathological analyses, are necessary for this, in order to clarify the diagnosis of fetus in fetu. Conclusion. Fetus in fetu is a rare pathology with few cases diagnoses prenatally. It is mainly diagnosed during infancy. X-ray images and, in some cases, chromosome or histopathological analyses, are greatly important for definitive diagnoses. Cómo citar. Lubinus F, Zuñiga-Hadechni E, López L, Rueda-Hernández, CA. Fetus in fetu, presentación de dos casos: diagnóstico diferencial y revisión de la literatura. MedUNAB. 2020;23(3):464-470. doi: doi.org/10.29375/01237047.3685 Introdução. Fetus in fetu é uma entidade congénita rara em que existe um gémeo monozigótico que, na maioria dos casos, está incorporado no abdómen do irmão. A apresentação mais comum é uma massa retroperitoneal. A diferenciação diagnóstica entre fetus in fetu e teratoma é discutida. O objetivo deste trabalho é descrever o caso de dois pacientes com fetus in fetu, por meio de uma revisão reduzida da literatura sobre as suas hipóteses etiológicas e métodos de diagnóstico. Relato de casos. Dois casos são apresentados, o primeiro, é um bebê menor com distensão abdominal persistente, no qual foi sentida uma massa abdominal. O segundo caso é um recém-nascido com diagnóstico pré-natal de massa abdominal. Ambos os casos apresentam imagens radiológicas mostrando massa abdominal compatível com fetus in fetu, razão pela qual foram posteriormente operados para ressecção da massa. Discussão. É importante considerar esta patologia como diagnóstico diferencial da massa abdominal em pacientes infantis, uma vez que ser capaz de diferenciá-la de um teratoma maduro indicaria que se trata de uma alteração no desenvolvimento embriológico e não de uma patologia tumoral. Para isso, são necessários métodos de imagem e em alguns casos testes cromossômicos ou histopatológicos, a fim de esclarecer o diagnóstico do fetus in fetu. Conclusão. Fetus in fetu é uma patologia rara que é diagnosticado principalmente na infância, com poucos casos diagnosticados no pré-natal. As imagens radiológicas e, em alguns casos, os testes cromossômicos ou histopatológicos são de grande importância para o diagnóstico definitivo. Cómo citar. Lubinus F, Zuñiga-Hadechni E, López L, Rueda-Hernández, CA. Fetus in fetu, presentación de dos casos: diagnóstico diferencial y revisión de la literatura. MedUNAB. 2020;23(3):464-470. doi: doi.org/10.29375/01237047.3685

Abstract Background Fetus in fetu (FIF) is a rare congenital anomaly. The preoperative diagnosis of FIF and differentiating it from teratoma and other abdominal tumors can be challenging for radiologists. Clarification of the blood supply and the relationship with the surrounding vessels is especially helpful for successful surgery; however, multimode ultrasound (US) performed for FIF has rarely been explored. Here, we first report a “humanoid” FIF case diagnosed by multimode US examinations, with the use of contrast-enhanced ultrasound (CEUS) for clarifying the blood supply features. Case presentation A 25-day-old preterm male infant was referred to our hospital for surgery. The US and computed tomography (CT) examinations led to a diagnosis of teratoma at the local hospital. The laboratory workup at our hospital revealed an elevation of total bilirubin, direct bilirubin, indirect bilirubin, alpha-fetoprotein, and neuron-specific enolase levels. A precise diagnosis and differentiation from teratoma, hepatoblastoma, neuroblastoma and other abdominal tumors were needed. In addition, the blood supply and the relationship with the surrounding vessels needed clarification prior to surgery. Multimode US examinations were performed and the features of a “humanoid” FIF as well as the blood supply for the abdominal lesion of the infant were suggested by grayscale US, color Doppler flow imaging (CDFI), and CEUS. Furthermore, CDFI and CEUS revealed an aorta-like structure and umbilical cord-like blood vessels in the “humanoid” FIF, and the CEUS helped with marking the surface of the infant’s abdominal wall. To the best of our knowledge, this is the first case report of CEUS in FIF, and the blood supply was clearly demonstrated in the FIF. The intraoperative findings confirmed our multimode US findings and revealed a “humanoid” FIF. The infant quickly recovered after the operation and had no positive findings at the 2-year follow-up visit. Conclusions Multimode US was helpful in diagnosing the rare FIF without radiation exposure. Specifically, CEUS clearly demonstrated the limb branch vessel-like structures, the abdominal aorta-like structure and the blood supply, which was useful for the FIF diagnosis and for avoiding damage to important vessels during the operation.

Fetiform teratoma is a rare highly developed mature teratoma with organoid differentiation although it is not as developed as fetus in fetus which is the only differential diagnosis of this entity. It should be distinguished from the fetus in fetu by absence of the axial skeleton. A 6-month-old baby girl with a lumbar lump underwent ultrasonography, CT-scan and surgery. On imaging, a sac-like structure was noted in the lumbar region containing bowel segments, mesentery-like structure and few lymph nodes. The patient underwent surgery. The entire sac with its content were completely excised. Very few cases of fetiform teratoma have been reported in English literature however to the best of our knowledge lumbar fetiform teratoma has not been reported up to now. Highly developed teratoma is a diagnostic dilemma as it resembles fetus in fetu. The absence of a spinal axis differentiates this entity from the fetus in fetu.

Fetus in fetu (FIF) is a rare anomaly characterized by the presence of a monozygotic twin that becomes incorporated into the abdomen of its sibling during fetal development. FIF is a rare congenital condition typically identified in infancy. We present a case of FIF in a 16-year-old male, which is an extremely rare presentation during adolescence. Teratoma is one of the differentials; however, FIF can be distinguished from teratoma by the presence of a vertebral column, often accompanied by a proper arrangement of other organs or limbs around it. Computed tomography (CT) imaging preoperatively diagnosed the FIF, prompting the decision for exploratory laparotomy. Histopathological analysis confirmed the diagnosis of FIF. Surgical excision is considered the optimal treatment., Competing Interests: Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work., (Copyright © 2024, Sahoo et al.)

Background: Fetus in fetu is a rare condition in which a malformed fetus is found in the body of a living twin. The retroperitoneum is the most common location of this condition. However, the sacrococcygeal region is a rare site of the disease. The presence of vertebral bodies and limbs differentiates FIF from teratoma. Imaging modalities are important for diagnosing FIF.Case Presentation: A 12-months old boy was hospitalized because of a mass in the sacrococcygeal region. CT showed a large, complex mass with bony structure resembling sacrococcygeal bone, hip bone and the femur in the sacrococcygeal region of the boy. The blood supply of the mass was from the aorta of the host. MRI revealed the mass was connected with the dilated sacral canal of the host, which resulted in tethered cord. A preoperative diagnosis of FIF was made and surgery was performed to remove the mass. Surgical removal and subsequent pathological examination revealed the anencephalic fetus had limb buds and a sacrum but no axial skeleton, which supported the diagnosis of FIF. Conclusions CT and MRI played important roles in diagnosing FIF based on the location of the lesion. [ABSTRACT FROM AUTHOR]

Fetus in fetu (FIF) is an exceedingly rare congenital anomaly characterized by the presence of a partially developed fetus within the body of its twin. It is a rare entity with fewer than 200 cases documented worldwide. Typically presenting as an abdominal mass in early childhood, this condition remains a diagnostic challenge due to its infrequency and varied clinical manifestations. We present the case of a 1-year-old female child referred to the pediatric surgery department due to an abdominal mass detected by her parents. Physical examination revealed a firm, ill-defined mass in the right upper abdomen. Ultrasonography delineated a heterogeneous, calcified mass in the right upper quadrant. Laboratory investigations (complete blood count, viral markers), including tumor markers (AFP, beta-hCG), were within normal limits. A midline laparotomy was performed, and intraoperative findings revealed a well-encapsulated mass adherent to the retroperitoneum, adjacent to the liver. Careful dissection was carried out to preserve vital structures, and the mass was successfully removed without rupture. Histopathological examination confirmed the diagnosis of fetus in fetu, displaying a spectrum of tissues reminiscent of embryonic development, including skin, adnexal structures, brain tissue, mature cartilage, adipose tissue, bone marrow elements, and a partially developed vertebral column. After the surgical resection, the patient experienced an uneventful postoperative recovery. At one year of follow up the patient has shown no signs of recurrence. FIF is characterized by diagnostic challenges, often requiring postoperative histological confirmation. Histopathological examination confirmed the presence of FIF. Surgical excision, is crucial for favorable outcomes, especially in preventing potential complications. Comprehensive histopathological evaluation remains imperative for accurate diagnosis. [ABSTRACT FROM AUTHOR]

Abstract 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.

Fetus in fetu (FIF) is a rare congenital anomaly. Anomalies of inferior vena cava (IVC) in the host are rare and not reported in the literature. In this case report, the surgical management and the findings of a rare vascular anomaly of IVC in a 10-month-old male child with FIF are discussed. This case highlights the importance of antenatal ultrasonogram in the detection of FIF and to diligently look for structural anomalies of IVC in the host in such cases. [ABSTRACT FROM AUTHOR]

Fetus in fetu (FIF) is an extremely rare anomaly. It is predominantly seen retroperitoneally in 80% of cases but can present at atypical sites like the skull, sacrum, scrotum and the mouth. We reported a rare case of intracranial parasitic fetus. We described the prenatal and postnatal MRI findings of the case. There was no obvious spinal signal on the imaging findings at 35 weeks of gestation. However, the postnatal MRI revealed spinal column signal at 5 months and 11 days. [ABSTRACT FROM AUTHOR]

To the best of our knowledge there are fewer than ten cases of fetus in fetu which have been reported in English medical literature to date from Bangladesh. None of them has sufficient details on pathology. This is a pathology-focused report of a nine-year-old Bangladeshi girl with typical features of fetus in fetu. She presented with abdominal distention which was radiologically found to be a retroperitoneal mass and the diagnosis was later confirmed by histopathology.

Fetus in fetu is a rare congenital entity in which a deformed parasitic twin develops within the body of a living newborn or a child. Meanwhile, fetiform teratoma is a rare congenital disorder with high degree of organoid differentiation resembling fetus in fetu. We present two cases of the rare entities with two unusual locations. A 1-week-old baby boy with a large anterior abdominal mass underwent CT-scan. A large mass containing pelvic bones, femora, tibia, fibula, fused kidneys, urinary bladder, hepatic parenchyma, brain tissue and spinal cord was noted in the anterior abdominal wall. The liver parenchyma of the host twin was fused with the hepatic parenchyma of the parasitic twin. Another 6-month-old baby girl with a large lumbar lump underwent ultrasonography, CT-scan and surgery. On imaging, a sac-like structure was noted in the lumbar region containing bowel segments, mesentery-like structure and few lymph nodes. Both cases are rare congenital anomalies and are a diagnostic challenge. It has been described that the presence of axial skeleton and limb buds differentiates the fetus in fetu from the fetiform teratoma, therefor, the first case was diagnosed as fetus in fetu and the latter one as fetiform teratoma.

Background: Fetus in fetu (FIF) is a rare congenital anomaly. The preoperative diagnosis of FIF and differentiating it from teratoma and other abdominal tumors can be challenging for radiologists. Clarification of the blood supply and the relationship with the surrounding vessels is especially helpful for successful surgery; however, multimode ultrasound (US) performed for FIF has rarely been explored. Here, we first report a "humanoid" FIF case diagnosed by multimode US examinations, with the use of contrast-enhanced ultrasound (CEUS) for clarifying the blood supply features.Case Presentation: A 25-day-old preterm male infant was referred to our hospital for surgery. The US and computed tomography (CT) examinations led to a diagnosis of teratoma at the local hospital. The laboratory workup at our hospital revealed an elevation of total bilirubin, direct bilirubin, indirect bilirubin, alpha-fetoprotein, and neuron-specific enolase levels. A precise diagnosis and differentiation from teratoma, hepatoblastoma, neuroblastoma and other abdominal tumors were needed. In addition, the blood supply and the relationship with the surrounding vessels needed clarification prior to surgery. Multimode US examinations were performed and the features of a "humanoid" FIF as well as the blood supply for the abdominal lesion of the infant were suggested by grayscale US, color Doppler flow imaging (CDFI), and CEUS. Furthermore, CDFI and CEUS revealed an aorta-like structure and umbilical cord-like blood vessels in the "humanoid" FIF, and the CEUS helped with marking the surface of the infant's abdominal wall. To the best of our knowledge, this is the first case report of CEUS in FIF, and the blood supply was clearly demonstrated in the FIF. The intraoperative findings confirmed our multimode US findings and revealed a "humanoid" FIF. The infant quickly recovered after the operation and had no positive findings at the 2-year follow-up visit.Conclusions: Multimode US was helpful in diagnosing the rare FIF without radiation exposure. Specifically, CEUS clearly demonstrated the limb branch vessel-like structures, the abdominal aorta-like structure and the blood supply, which was useful for the FIF diagnosis and for avoiding damage to important vessels during the operation. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. 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. 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. [ABSTRACT FROM AUTHOR]

Intracranial fetus in fetu is an extremely rare entity in which a discrete vertebrate fetiform mass is found inside a diamniotic, monochorionic twin. It is a benign mass and can manifest with symptoms owing to mass effect. To establish the diagnosis, a vertebra must be present within the mass. A 5-year-old child presented at a multispecialty hospital with gradual weakness of both lower limbs. Magnetic resonance imaging of the brain revealed a midline intraventricular mass with lobulated margins having both cystic and fatty components with areas of blooming within. A provisional diagnosis of teratoma/primitive neuroectodermal tumor was made. The patient subsequently presented to our hospital with drowsiness and vomiting for 1 day. Noncontrast computed tomography revealed a mass of heterogeneous density occupying the third ventricle. The mass contained a few well-formed long bones representative of the appendicular skeleton and a vertebra-like bone representative of the axial skeleton, fulfilling the Willis criteria. A biopsy sample was taken from the mass; no malignant cells were seen on histopathologic examination. Based on noncontrast computed tomography findings of well-formed long bones and a vertebra and no significant increase in the size of the mass over 2 years, an intracranial fetus in fetu was diagnosed. Whenever bony structures are identified in an intracranial mass in a pediatric patient, we should always look for bones of the axial skeleton, as this finding will point toward a diagnosis of intracranial fetus in fetu and will help in differentiating it from teratoma, which can have malignant transformation. [ABSTRACT FROM AUTHOR]

Fetus in Fetu (FIF) is a rare congenital anomaly in which a malformed parasitic twin is found within the body of a living child or adult. In this case report, an 18 month-old male child presented with a large abdominal mass and failure to thrive. Imaging studies confirmed the presence of a large retroperitoneal fetus in fetu with significant mass effect of the adjacent structures. A surgical resection was performed and pathology confirmed the diagnosis. These rare cases have become more frequently reported and a review of the literature for the past 15 years will describe the demographics, updated genetic findings, pathology and outcomes of this unusual tumor. Recent findings will also discuss an infrequent association with teratomas that may warrant a longer follow-up for surveillance of malignancy.

Fetus in fetu is an extremely rare congenital anomaly. We describe the perinatal diagnosis and management of a fetus with oropharyngeal and cervical fetus in fetu. High-resolution ultrasonography with 3-dimensional rendering can identify increased risks of airway obstruction in utero. Early identification allows a multidisciplinary team to be assembled for a scheduled ex utero intrapartum treatment procedure. [ABSTRACT FROM AUTHOR]

Fetus in fetu is a rare clinical entity consisting of malformed fetus inside body of the living partner. It is a mass containing a vertebral axis and often other organs and/or limbs. Unlike other classical cases, this case was not having a vertebral axis but other clinico-pathological findings were suggestive of fetus in fetu. To include such types of cases, the traditional definition by Willis of fetus in fetu needs revision.

Parasitic twin is a rare malformation, which involves two fetuses attached to each other, whereby one of the pair is viable and develops into a mature embryo (the host twin) called the autosite, while the second twin (parasite) is usually nonviable, but survives on the host twin; the site and extend of their attachment are varied and may be associated with other congenital malformations. Its exact cause is not completely understood. Though, it has been reported in many countries, there is dearth of information on its occurrence in Nigeria. Therefore, we report two cases of parasitic twins seen in our institution. The first case had an extra-limb, scrotal mass projecting from the anterior abdominal wall, which also had an anterior abdominal wall defect below the extra-limb, while the second case had a sacroccoygeal mass which was a duplicate gluteal mass with malformed lower limb, digit with a toe nail projecting from it and an atrophic scrotal skin attached. Both cases had chest, spinal X-rays and abdominal ultrasounds, which excluded any other malformation. They had successful surgical excision of parasites and are being followed-up in the surgical clinic both having appropriate developmental milestones.

Fetus in fetu (FIF) is a rare anomaly of diamniotic monochorionic twins, where a malformed fetus resides within the body of its twin. Most FIF occurs in the retroperitoneal region around the host spine and appears prenatally as a solid-cystic mass consisting of fetal-like structures. Imaging has an important role in the diagnosis of FIF. The present study reported a single case, a 45-year-old woman, with a teratoma in a third-trimester fetus diagnosed after prenatal ultrasonography (US), which showed a mass containing fetus-like echoes. FIF was considered after the US showed that the mixed solid-cystic retroperitoneal mass around the vertebral axis of the host fetus consisted of two separate masses, each containing distinct fetal visceral structures. One fetus was acardiac and the other parasitic fetus was visible with a weak heartbeat. Postpartum magnetic resonance imaging and ultrasonography (US) scans of the newborn showed a retroperitoneal cystic space-occupying mass with distinctive limbs and visceral structures. The pathological examination further confirmed the diagnosis of retroperitoneal FIF. Also, a prenatal US could detect FIF in utero. A cystic-solid mass containing long bones, vascular pedicles, or visceral structures around the vertebral axis of the host fetus in the US might suggest the possibility of a FIF. [ABSTRACT FROM AUTHOR]

Fetus in fetu is an uncommon medical anomaly characterized by the presence of a malformed fetus within the body of a living twin. Although the retroperitoneum is the most typical location, occurrences in the sacrococcygeal and dorsolumbar regions are rare. Ongoing debates center around its embryopathogenesis, debating whether it is a highly specialized teratoma or a result of parasitic twinning in a monozygotic monochorionic diamniotic pregnancy. Notably, distinguishing factors such as vertebral bodies and limbs are pivotal in discerning FIF from teratomas. Diagnostic imaging techniques are integral for preoperative diagnosis, with histopathological examination confirming the condition's presence., Competing Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article., (© The Author(s) 2023.)