Journal of Perinatology (2006) 26, 366–367 r 2006 Nature Publishing Group All rights reserved. 0743-8346/06 $30 www.nature.com/jp IMAGING CASEBOOK Prenatal diagnosis of a neonate with fetus in fetu R Tiwari1, K Hicks2, M Naqvi1, E Biskinis1, J Nirgiotis1, J Van Hook3 and R Suffield3 1Department of Pediatrics, Texas Tech University Health Sciences Center at Amarillo, Amarillo, TX, USA; 2Texas Tech University Health Sciences Center at Amarillo, School of Medicine, Amarillo, TX, USA and 3Department of Obstetrics and Gynecology, Texas Tech University Health Sciences Center at Amarillo, Amarillo, TX, USA mass within the mid abdomen with displacement of the central Fetus in fetu is a rare condition not usually considered in the differential of bowel. A computed tomography scan of the abdomen and pelvis a neonatal abdominal mass. This article illustrates the importance of revealed a large cystic mass of size 6.4 Â 3.4 Â 4.2 cm3 prenatal ultrasound in the treatment of this condition as it facilitated the compressing the adjacent bowel. The mass also contained bony assembily of a multispecialty healthcare team that intervened within days of fragments, which appeared to be remnants of a second fetus. The birth. liver, kidney, and spleen appeared normal. Journal of Perinatology (2006) 26, 366–367. doi:10.1038/sj.jp.7211514 The patient was operated on DOL 2. The mass was in the retropancreatic area and attached to the small bowel. The gross specimen showed a fetal remnant (Supplementary Figure 2). Introduction Pathological analysis of the resected mass grossly described a Prenatal ultrasound allows for the identification of abnormalities 5.5 Â 3.0 Â 2.5 cm3 malformed second fetus encased within a that could potentially complicate the neonatal period of life. Thus, membranous covering. The membrane was consistent with a fetal neonatologists and obstetricians can anticipate the needs of the sac containing a chorionic membrane and epithelium with a neonate and decrease morbidity. An abdominal mass detected on marked similarity to amnion. The mass had two lower extremities, prenatal ultrasound has an exceedingly wide differential diagnosis, of which one foot had three toes and the other foot had two toes, as and fetus in fetu (FIF) is not a disease entity normally considered. well as buttocks and male genitalia. These lower limbs were The following case report discusses the condition of FIF, its covered by epidermis and a dermis complete with hair follicles. differentiation from the more common diagnosis of teratoma, and Skeletal muscle was evident. Bone and cartilage were present in the benefits of early detection. each limb. No head or upper extremities were clearly recognizable. A radiograph of the gross specimen was taken. The mass was confirmed to be an endoparasitic twin as it showed a vertebral Case report column, and the microscopic tissue sections showed well organized and developing tissue. The microscopic sections through the A 2803 g 37-week male delivered vaginally was admitted to the anencephalic brain showed well-organized neural tissue. Sections NICU with a history of abdominal mass diagnosed by prenatal through the area surrounding the umbilicus showed small bowel. ultrasound. The mother was a 26-year-old gravida 3, para 3 Hispanic female. Her prenatal course was uneventful except for an abnormal prenatal ultrasound, which showed an intra-abdominal fetal mass in the mid upper abdomen. The mass was cystic, with a Discussion centrally located fetus and placenta (Figure 1). Apgar scores were 8 Fetus in fetu, the presence of one twin trapped within the at 1 min and 9 at 5 min. Cord blood pH was 7.36. The baby had no developing confines of its sibling and acting as a parasite of the dysmorphic features. The lungs revealed minimal retained lung dominant twin’s fetal circulation, is a rare clinical entity. As of fluid. Abdominal examination revealed no distention, although a 2004, 88 cases have been reported,1 and recent cases have firm mass was palpable in the mid abdomen. The remainder of the diagnosed FIF in the prenatal period using advanced sonography.2 exam was benign. A postnatal abdominal radiograph revealed a The pathologic diagnosis is confirmed by the presence of a vertebral column, well-differentiated organs, and limb buds.3 Other Correspondence: Dr R Tiwari, Department of Pediatrics, Texas Tech University Health Sciences Center at Amarillo, PGY3, 1400 S Coulter Road, Amarillo, TX 79106, USA. criteria in the diagnosis of FIF include the presence of a capsule or E-mail: [email protected] fetal membranous covering, vascular connections, skin 4 There were no sources of financial assistance. differentiation, and an umbilical cord with two vessels. The most Received 21 March 2006; accepted 23 March 2006 common location of FIF is retroperitoneal; indeed, 80% of cases Prenatal diagnosis of FIF R Tiwari et al 367 earlier intervention within the neonatal period as opposed to childhood or adulthood. The prenatal ultrasound for this case reported a mass consistent with the characteristics of FIF. In accordance with recommendations of a recent case diagnosed prenatally,6 prompt induction of delivery was instituted and surgical intervention occurred. Currently, computed tomography is part of the standard of care and performed in the majority of FIF cases. The presence of a vertebral column on a preoperative computed tomography can aid in the definitive diagnosis of FIF before the operation. Before the advent of computed tomography, only 16.7% of cases were able to predict the diagnosis of FIF before surgical intervention.4 In the present case, computed tomography was unable to detect a vertebral column. A radiograph of the Figure 1 Prenatal ultrasound of pelvis and abdomen. The figure surgical specimen showed a segment of a vertebral column. shows an intra-abdominal fetal mass in the mid upper abdomen. The Ultimately, prenatal ultrasound was the significant instrument, mass is cystic, with a centrally located fetus and placenta. which strongly suggested the diagnosis of FIF, and the specific criteria for FIF were fulfilled after pathologic and radiologic analysis of the surgical specimen. have followed this pattern.4 Other rare locations include the oral This case report elucidates the presentation and pathology of cavity, lumbar region, and cranium.4 FIF. Prenatal ultrasound allowed for diagnosis and immediate The differential diagnosis of FIF includes neoplasia, most intervention, which makes this case one of the few cases dealt with commonly a mature teratoma, and pseudocyst. Higher levels of in this manner. tissue differentiation, such as organ development, and the vertebral column distinguish FIF from teratoma. Willis did not consider FIF to be an extremely well-developed teratoma and the argument References 5,1 continues as to whether FIF belongs on the teratoma continum. 1 Brand A, Alves MC, Saraiva C, Loio P, Goulao J, Malta J et al. Fetus in fetu Like FIF, teratomas are masses of well-composed tissues and cells – diagnostic criteria and differential diagnosis – a case report and but lack organization to the point of organ development. literature review. J Pediatr Surg 2004; 39(4): 616–618. Teratomas also lack vertebral columns, which is the central 2 Chen CP, Chern SR, Liu FF, Jan SW, Lee HC, Sheu JC et al. Prenatal distinction from FIF. Fetus in fetu occurs when an error in cell diagnosis, pathology, and genetic study of fetus in fetu. Prenatal Diagn division of the early blastocyst allows for one twin to become 1997; 17(1): 13–21. entrapped within the cell mass of the other twin.4 The subordinant 3 Talerman A. Germ cell tumors of the ovary. In: Kurman RJ (ed.) twin becomes dependent on the dominant twin. Thus, the fully Blaustein’s Pathology of the Female Genital Tract. 5th edn. Springer- developed twin acts as a host to its immature twin, which is Verlag: New York, 2002 pp 967–1033. contained inside the body cavity of the dominant twin and attached 4 Hoeffel CC, Nguyen KQ, Phan HT, Truong NH, Nguyen TS, Tran TT et al. Fetus in fetu: a case report and literature review. Pediatrics 2000; 105(6): to the vitelline circulation of the dominant twin. 1335–1344. The detection of FIF can be made during the prenatal period as 5 Willis RA. Structure of teratomata. J Pathol Bacteriol 1935; 40(January): in the current case. Very few cases have been diagnosed using 1–36. sonogram with the current literature suggesting about five cases 6 Mills P, Bornick PW, Morales WJ, Allen M, Gilbert-Barness E, Johnson PK 6 thus discovered. Eighty nine percent of cases are discovered before et al. Ultrasound prenatal diagnosis of fetus in fetu. Ultrasound Obstet the child reaches 18 months,4 but ultrasound can allow for even Gynecol 2001; 18(1): 69–71. Supplementary Information accompanies the paper on the Journal of Perinatology website (http://www.nature.com/jp) Journal of Perinatology.