Fetal for Wednesday, April 9th, 2025

History

30-year-old patient presenting for 20 weeks fetal anatomy scan, level 2 prenatal ultrasound
Right pelvic complex cystic fetal mass noted at 20weeks and 6days estimated gestational age (EGA)
Patient referred to the Perinatal and Fetal Cardiology Programs-Nemours Children’s Health Delaware
Fetal MRI and repeat ultrasounds performed
Postnatal imaging performed
Surgical resection with pathologic correlation

Images (Click any image to enlarge)

Question

What is the diagnosis of the complex cystic lesion in the fetus and then neonate after birth?

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Correct answer

Fetus in fetu

Discussion

Complex pelvic cystic and solid lesion in the female fetus is seen at the anatomy scan. 

Hyperechoic and partially anechoic focus containing mixed echogenicity with soft tissue and hyperechoic
attenuation, osseous structures, identified on both prenatal and postnatal ultrasound.

Rudimentary pelvic bones, lower extremities bones, and dysmorphic vertebral elements are identified on prenatal ultrasound and Fetal MR. Similar findings are identified on postnatal imaging including radiograph, ultrasound, and CT scan of the pelvis.

Diagnosis of Fetus in fetu:

Fetus in fetu occupying the fetal right ovary with near complete skeleton and underdeveloped brain and spinal cord. 

Differential diagnosis

1. Fetus in fetu: Organization of the tissues and bone, not a random assortment of structures, neural axis elements, organs

2. Teratoma

3. Complex ovarian cyst

4. Meconium pseudocyst

5. GI duplication cyst

6. Urachal cyst

References

• Harigovind D, Babu SP, Nair SV, Sangram N, Fetus in fetu – a rare developmental anomaly, Radiology Case Reports, Volume 14, Issue 3, 2019, Pages 333-336, ISSN 1930-0433.
• Gangopadhyay AN, Srivastava A, Srivastava P.et al. Twin fetus in fetu in a child: a case report and review of the literature. J Med Case Reports 4, 96 (2010).
• Ruffo G, Di Meglio L, Di Meglio L, Sica C, Resta A, Cicatiello R. Fetus-in-fetu: two case reports. J Matern Fetal Neonatal Med. 2019 Sep;32(17):2812-2819. doi: 10.1080/14767058.2018.1449207. Epub 2018 May 27. PMID: 29804477.
• Taher HMA, Abdellatif M, Wishahy AMK, Waheeb S, Saadeldin Y, Kaddah S, Abdulsattar AH, Osman MA, El Tagy GH, Elbarbary MM, Khairi A, Tawfik S, Anis S, Anis E, Farouk M, Abdelfattah AH, Muensterer OJ. Fetus in Fetu: Lessons Learned from a Large Multicenter Cohort Study. Eur J Pediatr Surg. 2020 Aug;30(4):343-349. Epub 2019 Nov 26. PMID: 31770783.
• Sharma A, Goyal A, Sharma S. Fetus in fetu: A rare case report. J Res Med Sci. 2012 May;17(5):491-4. PMID: 23626618; PMCID: PMC3634279.
• Patankar T, Fatterpekar GM, Prasad S, Maniyar A, Mukherji SK: Fetus in fetu: CT appearance: report of two cases. Radiology 2000; 214: pp. 735-737.
• Hong SS, Goo HW, Jung MR, Kim HJ, Kim EA, Kim KS, et. al.: Fetus in fetu: three-dimensional imaging using multidetector CT. AJR Am J Roentgenol 2002; 179: pp. 1481-1483.
• Brand A, Alves MC, Saraiva C, Loío P, Goulão J, Malta J, et. al.: Fetus in fetu—diagnostic criteria and differential diagnosis: a case report and literature review. J Pediatr Surg 2004; 39: pp. 616-618.