Fetus in fetu - a rare developmental anomaly

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.

External fetus in fetu presenting in the second trimester: A case report and literature review

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.

Retroperitoneal fetus in fetu presenting in a male infant: A case report and literature review

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.

A cohort of five cases with asymmetric conjoined twining and literature review

PURPOSE

Asymmetric conjoined twining (ACT) is a form of conjoined twining which is a rare malformation of monochorionic monoamniotic twin pregnancy. Most publications were single case reports. We reported a cohort of five cases with ACT from a single tertiary medical center and reviewed the case reports of ACT over the last decade to enrich the clinical research of this disease and summarized the clinical features of the disease.

METHODS

We reviewed five cases of ACT admitted in Tianjin Children's Hospital from 17 March, 2008, through 7 March 2017. The cohort was analysed from general information, imaging manifestations, separation surgery, histopathological findings, outcome and follow-up. We searched the English literatures on case reports of ACT over the past decade from the PubMed database and presented details about the clinical characteristics, treatment, and prognosis of all cases.

RESULTS

There were four males and one female in our cohort. Among the five cases, two parasites were located in epigastrium, two in rachis, and one in retroperitoneum (fetus in fetu, FIF). All of the parasites were separated successfully by operation in five cases and were confirmed to be ACT by histopathology reports. Four patients made an uneventful recovery except for one case of wound infection. All of them were doing well in follow-up. In the literature review, we found 41 cases of exoparasitic heteropagus twining (EHT) and 63 cases of FIF.

CONCLUSIONS

ACT is very rare and usually diagnosed by prenatal ultrasonography (US). Computed tomography (CT) and magnetic resonance imaging (MRI) examinations are essential imaging examinations before separation surgery to delineate the anatomical relationship between the autosite and the parasite. In general, the separation surgery of ACT is less complicated and the prognosis is better compared with the symmetric conjoined twining (SCT).

Retroperitoneal parasitic fetus: A case report

BACKGROUND

Fetus-in-fetu (FIF) is an extremely rare congenital abnormal mass, in which a normal fetus’s vertebral axis frequently connected with malformed fetus around this axis. Here, we report the case of a male infant aged 26 d presenting with retroperitoneal parasitic fetus.

CASE SUMMARY

In a prenatal examination, we first detected an abdominal mass measuring 7.8 cm × 5.1 cm × 6.8 cm in a mother’s abdomen at 25 gestational weeks and teratoma was suspected. After the fetal was born, we did a magnetic resonance imaging (MRI) and ultrasonography on him and saw a distinctive limb with five-toes. According to the result of MRI, ultrasonography and postoperative pathology, he finally was diagnosed with FIF.

CONCLUSION

A laparotomy was performed at 26 d of age with excision of the retroperitoneal cystic tumor, which measured about 10 cm in diameter. According to the result of imaging and histological test, FIF was confirmed.

A rare case of fetus in fetu in the sacrococcygeal region: CT and MRI findings

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.

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.

Antenatal Diagnosis of Retroperitoneal Cystic Mass: Fetiform Teratoma or Fetus in Fetu? A Case Report

BACKGROUND Teratoma, a tumor containing a variety of tissues, is a broad diagnosis containing mature teratoma, immature teratoma, and teratomas with malignant transformation. The tumor forms during embryological development secondary to unsuccessful migration of primordial germ cells. A specific type of mature teratoma, containing human-like features, is called a fetiform teratoma. The fetiform teratoma is often compared and confused with fetus in fetu, a reabsorbed twin. While these tumors have commonly been described in the gonads, the retroperitoneal location finding on antenatal imaging is rare. The distinction between the aforementioned subtypes is not well established, proving a challenging diagnosis prior to resection. CASE REPORT We present a case of a newborn male with a prenatal diagnosis of retroperitoneal cystic mass. Although prenatal imaging was obtained, the diagnosis remained unclear. After birth, planned surgical excision on day of life 7 showed the suprarenal mass contained contiguous intestinal elements. Histopathology examination revealed a mature cystic teratoma with multiple tissue types, including colonic, brain, respiratory, lymphatics, and nerves, reminiscent of fetiform teratoma. This case report presents an interesting example of differentiating elements straddling the diagnoses mentioned above. CONCLUSIONS This is the first reported case of fetiform teratoma diagnosed in a newborn and is especially unique for having the element of intestinal duplication within the retroperitoneal mass. The differentiating features of fetus in fetu and fetiform teratoma depend on subjective distinctions. The case provides an opportunity to discuss the differentials and management strategies.

Intracranial Fetus In Fetu-a Pediatric Rarity

BACKGROUND

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.

CASE DESCRIPTION

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.

CONCLUSIONS

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.