Imaging findings in Fetus-in-fetu-misdiagnosed commonly as teratoma

Rajakumar R., Annu Singhal, Sana Sana, Kavita Vani


Fetus in fetu is a rare condition associated with abnormal embryogenesis in a diamniotic, monochorionic pregnancy, wherein one of the fetus is enclosed within the body of another normally developing fetus. It should be differentiated from a teratoma because of the later’s malignant potential. Here we report a case of 2 months old girl child who presented with complaints of abdominal distension. USG showed a solid cystic retroperitoneal mass resembling an anencephalic fetus. Contrast enhanced Computed tomography (CT) showed similar findings with visualization of bones resembling femur, sacrum and vertebrae. Findings were correlated with MRI and post-op pathology. The preoperative diagnosis of FIF is based on the observation of vertebral column or limbs in a mass on imaging modalities and our case meets the required criteria.


Fetus-in-fetu, teratoma, Ultrasonography, Computed tomography, Magnetic resonance imaging

Full Text:



Harigovind D, Sp HB, Nair SV, Sangram N. Fetus in fetu–a rare developmental anomaly. Radiology case reports. 2019;14(3):333-6.

Miura S, Miura K, Yamamoto T, Yamanaka M, Saito K, Hirabuki T et al. Origin and mechanisms of formation of fetus‐in‐fetu: Two cases with genotype and methylation analyses. American Journal of Medical Genetics Part A. 2006;140(16):1737-43.

Ji Y, Chen S, Zhong L, Jiang X, Jin S, Kong F et al. Fetus in fetu: two case reports and literature review. BMC pediatrics. 2014;14(1):1-6.

Matsubara N, Akasaka Y, Kanagaki M, Okamoto S. A case report of fetus in fetu with an aorta-like structure visualized by contrast-enhanced CT. Radiology Case Reports. 2020;15(12):2645-8.

Hopkins KL, Dickson PK, Ball TI, Ricketts RR, O'Shea PA, Abramowsky CR. Fetus-in-fetu with malignant recurrence. Journal of pediatric surgery. 1997;32(10):1476-9.

Khalifa NM, Maximous DW, Abd-Elsayed AA. Fetus in fetu: a case report. Journal of Medical Case Reports. 2008;2(1):1-3.

Jones DC, Reyes-Múgica M, Gallagher PG, Fricks P, Touloukian RJ, Copel JA. Three‐dimensional sonographic imaging of a highly developed fetus in fetu with spontaneous movement of the extremities. Journal of ultrasound in medicine. 2001;20(12):1357-63.

Landmann A, Calisto JL, Reyes-Múgica M, Thomas D, Malek MM. Fetus-in-Fetu presenting as a cryptorchid testis and abdominal mass: a report of a case and review of the literature. Journal of Pediatric Surgery Case Reports. 2016;13:38-40.

Gangopadhyay AN, Srivastava A, Srivastava P, Gupta DK, Sharma SP, Kumar V. Twin fetus in fetu in a child: a case report and review of the literature. Journal of medical case reports. 2010;4(1):1-7.

Hoeffel CC, Nguyen KQ, Phan HT, Truong NH, Sao Nguyen T, Tran TT et al. Fetus in fetu: a case report and literature review. Pediatrics. 2000;105(6):1335-44.

Willis RA. The borderland of embryology and pathology. The borderland of embryology and pathology. 1958.