Case report: fetus-in-fetu--imaging, surgical and pathological findings

Fetus in fetu from newborn's mediastinum: case report and a review of literature

Fetus in fetu is a rare congenital anomaly, when the malformed monozygotic twin is found within the body of a living child or sometimes in an adult. We report a case of fetus in fetu diagnosed during the early third trimester of pregnancy, in the medial and inferior portions of anterior mediastinum of the dominant twin. The diagnosis was suspected by prenatal ultrasound and fetal magnetic resonance imaging. It was postnatally confirmed by CT and RTG, surgically removed after birth and histologically examined. Histologically we found well-developed organs and tissues derived from all germ layers. To our knowledge, we describe the fourth case of fetus in fetu located in the thorax, and the second case located in the anterior mediastinum. This case highlights the usefulness of prenatal ultrasound and MRI in the diagnosis of mediastinal masses, and the usefulness of complete histological examination for confirmation of diagnosis of fetus in fetu. We also reviewed the possible embryologic backgrounds of this congenital anomaly.

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.

Oropharyngeal fetus in fetu

Fetus in fetu is an extremely rare entity and refers to the growth of a "parasitic" twin within a more mature fetus due to its inclusion within cells of the blastocyst. The presence of a vertebral column is considered essential for the diagnosis of a fetus in fetu. The retroperitoneum is the most common location for a fetus in fetu and its location in the mouth is rare. We report a case of oropharyngeal mass detected on antenatal sonography with imaging features consistent with a fetus in fetu. Complete surgical removal of the mass was aided by imaging. Follow-up of these patients is recommended to detect the rare incidence of malignant degeneration.

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.

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

The authors report the third case since 1964 of fetus-in-fetu presenting at Red Cross Children's Hospital. A fetal liver abnormality was detected during routine antenatal ultrasound scan, and the postnatal diagnosis of an intrahepatic, multiple fetus-in-fetu was made with abdominal ultrasound scan, plain radiograph of the abdomen and computed tomography. The mass was removed surgically by hemihepatectomy when the patient was 4 months of age. Imaging and the macroscopic and microscopic appearances of the abnormality confirmed the diagnosis and amplified it to include an adjacent teratoma. Multiple small subcapsular and perimass vascular hamartomas were coincidentally discovered in the liver. Two of the 3 nodules within the amniotic-lined cavity of the intrahepatic mass individually comply with the accepted criteria for fetus-in-fetu, and the third nodule has the accepted features of a benign teratoma. The existence of multiple fetus-in-fetu and fetus-in-fetu combined with a teratoma, is recorded in the medical literature. The imaging as well as the macroscopic and microscopic features are illustrated.

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.