Fetus in fetu

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Anteroposterior abdominal radiograph shows a soft-tissue mass in the right hemiabdomen. The mass contains calcified osseous-appearing structures of varying sizes and shapes.
The postoperative specimen shows a fairly well developed fetus lying on its back, with rudimentary digits.
Computed Tomography scan of the patient's abdomen reveals a large retroperitoneal soft-tissue mass. There are long hyperdense opacities that resemble fetal bones.

Fetus in fetu (or foetus in foetu) is a developmental abnormality in which a mass of tissue resembling a fetus forms inside the body. There are two theories of origin concerning "fetus in fetu". One theory is that the mass begins as a normal fetus but becomes enveloped inside its twin.[1] The other theory is that the mass is a highly developed teratoma. "Fetus in fetu" is estimated to occur in 1 in 500,000 live births.[2]

Classification as life[edit]

A fetus in fetu can be considered alive, but only in the sense that its component tissues have not yet died or been eliminated. Thus, the life of a fetus in fetu is akin to that of a tumor in that its cells remain viable by way of normal metabolic activity. However, without the gestational conditions in utero with the amnion and placenta, a fetus in fetu can develop into, at best, an especially well differentiated teratoma; or, at worst, a high-grade metastatic teratocarcinoma. In terms of physical maturation, its organs have a working blood supply from the host, but all cases of fetus in fetu present critical defects, such as no functional brain, heart, lungs, gastrointestinal tract, or urinary tract. Accordingly, while a fetus in fetu can share select morphological features with a normal fetus, it has no prospect of any life outside of the host twin. Moreover, it poses clear threats to the life of the host twin on whom its own life depends.[3]

Theories of development[edit]

There are two main theories about the development of fetus in fetu; one simple, the other complex.

Teratoma theory[edit]

Main article: Teratoma

Fetus in fetu may be a very highly differentiated form of dermoid cyst, itself a highly differentiated form of mature teratoma.[4]

Parasitic twin theory[edit]

Main article: Parasitic twin

Fetus in fetu may be a parasitic twin fetus growing within his or her host twin. Very early in a monozygotic twin pregnancy, in which both fetuses share a common placenta, one fetus wraps around and envelops the other. The enveloped twin becomes a parasite, in that his or her survival depends on the survival of his or her host twin, by drawing on the host twin's blood supply. The parasitic twin is anencephalic (without a brain) and lacks some internal organs, and as such is almost always unable to survive on its own. As the normal twin has to "feed" the enveloped twin from the nutrients received over a single umbilical cord, he or she usually dies before birth.[citation needed]

Examples from history and in the media[edit]

An early example of the phenomenon was described in 1808 by George William Young. [5]

Cases of fetus in fetu sometimes attract worldwide media attention. These cases are a small minority of the known cases and rarely overlap with cases reported in the medical literature, but they are widely accessible.

Examples in fiction[edit]


  1. ^ Chua, JHY; Chui CH, Sai Prasad TR et al. (2005). "Fetus-in-fetu in the pelvis" (PDF). Annals of the Academy of Medicine Singapore 34: 646–9. 
  2. ^ Grant P, Pearn JH (May 1969). "Foetus-in-foetu". Med. J. Aust. 1 (20): 1016–9. PMID 5815070.  — source not consulted; cited here following Hoeffel CC, Nguyen KQ, Phan HT, et al. (June 2000). "Fetus in fetu: a case report and literature review". Pediatrics 105 (6): 1335–44. doi:10.1542/peds.105.6.1335. PMID 10835078. 
  3. ^ "Journal of Medical Case Reports | Full text | Fetus in fetu : a case report". Jmedicalcasereports.com. Retrieved 2012-11-22. 
  4. ^ Basu A, Jagdish S, Iyengar KR, Basu D (October 2006). "Fetus in fetu or differentiated teratomas?". Indian J Pathol Microbiol 49 (4): 563–5. PMID 17183856. 
  5. ^ George William Young (1608). "Case of A Foetus found in the Abdomen of a Boy". Ncbi.nlm.gov. Retrieved 2012-11-22. 
  6. ^ "Man With Twin Living Inside Him - A Medical Mystery Classic - ABC News". Abcnews.go.com. 2006-08-23. Retrieved 2012-11-22. 
  7. ^ Alok Jha. "How did that boy end up with his twin growing inside him? (July 17, 2003) | Science | Retrieved 23 May 2014". London: The Guardian. 
  8. ^ "Science, Nature and the Environment". Channel 4. Retrieved 2012-11-22. 
  9. ^ "Surgeons remove two fetuses from infant - Health | NBC News". MSNBC. 2006-03-28. Retrieved 2012-11-22. 
  10. ^ "Boy born with fetus in his stomach - Health - Health care - More health news | NBC News". MSNBC. 2006-11-24. Retrieved 2012-11-22. 
  11. ^ "Fetus inside a baby; 'broken' food | Public Affairs | GMA News Online | The Go-To Site for Filipinos Everywhere". Gmanews.tv. 2007-08-01. Retrieved 2012-11-22. 
  12. ^ "Bearing Your Own Twin - ABC News". Abcnews.go.com. 2008-05-16. Retrieved 2012-11-22. 
  13. ^ Thomson, Katherine (June 10, 2008). "Baby Born With Second Penis On Back (PHOTO)". Huffington Post. 
  14. ^ "'I've never seen anything like it,' doctor says of newborn's brain surgery | brain, sam, doctor - Top Stories - Colorado Springs Gazette, CO". Gazette.com. 2008-12-15. Retrieved 2012-11-22. 
  15. ^ "Baby born with 'foot in brain'". BBC (London). December 19, 2008. Retrieved 2008-12-21. "US surgeons operating on a brain tumour in a baby boy found a tiny foot inside his head." 
  16. ^ "China's Kang Mengru survives twin foetus removal in Zhenzhou | Mail Online". London: Dailymail.co.uk. 2009-09-22. Retrieved 2012-11-22. 
  17. ^ "Report of a Case and Literature Review : Fetus in Fetu Laki-laki Hamil Selama 41 Tahun ( Pregnancy in Male For About 41 Years ) « Dr Herry S Yudha Utama SpB MHKes FInaCS". Herrysetyayudha.wordpress.com. 2011-11-23. Retrieved 2012-11-22. 
  18. ^ Dr. Herry Setya Yudha Utama SpB MHKes FInaCS ICS (2011-11-22). "Dr Herry Setya Yudha Utama SpB. MHKes. FInaCS. ICS: Case Report and Literatur Review : Fetus in Fetu Laki-laki Hamil Selama 41 Tahun ( Pregnancy in Male For About 41 Years )". Herryyudha.blogspot.com. Retrieved 2012-11-22. 
  19. ^ Clee, Nicholas (2007-03-02). "The marriage of music and science". The Guardian (London). 
  20. ^ "Dr. Jin Episode 22 (hulu)". Dramastyle. Retrieved 2012-11-22. 

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