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{{Short description|Fetus-like mass within the body of its twin}}
⚫ {{main|Teratoma}}
{{Italic title|string=in fetu}}
⚫ {{main|Parasitic twin}}
]
]
] scan of the same patient's abdomen pre-operation 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 rare ] in which a mass of tissue resembling a ] forms inside the body of its ]. An early example of the phenomenon was described in 1808 by George William Young.<ref>{{cite journal | vauthors = Young GW | title = Case of a Fœtus found in the Abdomen of a Boy | journal = Medico-Chirurgical Transactions | volume = 1 | pages = 236–264 | date = 1808 | pmid = 20895115 | pmc = 2128792 }}</ref>
'''Fetus in fetu''' (or '''''fœtus in fœtu''''') describes an extremely rare abnormality classified as a ] containing entire organ systems, even major body parts such as torso or limbs. It has often been interpreted as a ] growing within its ]. It is one of the most extreme forms of ]. The condition occurs in 1 in 500,000 live births.<ref name=msnbc1>], ], accessed ], ]]</ref>{{verify credibility}}<!-- The claimed incidence 1:500,000 is not original to MSNBC; the original scholarly source of this claim needs to be found and read, to decide if it is credible. -->


There are two hypotheses for the origin of a fetus ''in fetu''. One hypothesis is that the mass begins as a normal fetus but becomes enveloped inside its twin.<ref name="Chua">{{cite journal| vauthors = Chua JH, Chui CH, Sai Prasad TR |title=Fetus-in-fetu in the pelvis |journal=Annals of the Academy of Medicine Singapore |volume=34 |pages=646–9 |year=2005 |doi=10.47102/annals-acadmedsg.V34N10p646 |url=http://annals.edu.sg/pdf/34VolNo10200511/V34N10p646.pdf |display-authors=etal |url-status=dead |archive-url=https://web.archive.org/web/20071011012449/http://annals.edu.sg/pdf/34VolNo10200511/V34N10p646.pdf |archive-date=2007-10-11 }}</ref> The other hypothesis is that the mass is a highly developed ]. Fetus ''in fetu'' is estimated to occur in 1 in 500,000 live births.<ref>{{cite journal | vauthors = Grant P, Pearn JH | title = Foetus-in-foetu | journal = The Medical Journal of Australia | volume = 1 | issue = 20 | pages = 1016–1019 | date = May 1969 | pmid = 5815070 | doi = 10.5694/j.1326-5377.1969.tb49866.x | s2cid = 209072187 }}<!-- someone needs to read this paper for evidence supporting what happento vero ayerthe claimed incidence --> — source not consulted; cited here following {{cite journal | vauthors = Hoeffel CC, Nguyen KQ, Phan HT, Truong NH, Nguyen TS, Tran TT, Fornes P | title = Fetus in fetu: a case report and literature review | journal = Pediatrics | volume = 105 | issue = 6 | pages = 1335–1344 | date = June 2000 | pmid = 10835078 | doi = 10.1542/peds.105.6.1335 }}</ref>
==Development==
⚫ Fetus in fetu starts to develop very early in a monozygotic twin pregnancy, in which both fetuses share a common placenta, and one fetus wraps around and envelops the other. The enveloped twin becomes a ], in that its survival depends on the survival of its host twin, by drawing on the host twin's blood supply. Invariably the parasitic twin is ] (without a ]) and lacks some ], and as such is unable to survive on its own. The parasitic twin sometimes grows large enough to kill its host twin, in which case both twins die.<ref name=kirch>], accessed ], ]]</ref>{{verify credibility}}


== Classification as life ==
Sometimes, however, the host twin survives and is delivered. It continues to survive until it grows so large that it starts to harm the host, at which point ] usually intervene.<ref name=abc1/>{{verify credibility}} The condition causes the host to look like they are ] (since they technically are) and can occur in both males and females.
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 ] in that its cells remain viable by way of normal metabolic activity. However, without the gestational conditions ''in ]'' with the ] and ], a fetus ''in fetu'' can develop into, at best, an especially well ]; or, at worst, a high-grade ] ]. 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 ] 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.<ref>{{cite journal | vauthors = Khalifa NM, Maximous DW, Abd-Elsayed AA | title = Fetus in fetu: a case report | journal = Journal of Medical Case Reports | volume = 2 | issue = 1 | pages = 2 | date = January 2008 | pmid = 18186928 | pmc = 2253549 | doi = 10.1186/1752-1947-2-2 | publisher = Jmedicalcasereports.com | doi-access = free }}</ref>


== Hypotheses of development ==
This condition can be psychologically extremely disturbing for the person who receives a diagnosis of fetus in fetu, or even of an ordinary ].
There are two main hypotheses about the development of fetus ''in fetu''.


=== Teratoma hypothesis ===
==Examples==
⚫ {{Main|Teratoma}}
*'''Alamjan Nematilaev''' was the surviving host of a Fetus in fetu. In 2003, aged 7, his school ] in ] referred him to hospital after movements were detected in the boy's enlarged stomach. An operation intended to remove a ] uncovered the fetus of Alamjan's identical twin brother, which had lived as parasitic growth inside the boy throughout his entire life. The fetus was comparatively highly developed, with ], arms, fingers, nails, legs, toes, genitals, a head, and a vague approximation of a face.<ref>], ], accessed ], ]]</ref><ref>], ]]</ref>
Fetus ''in fetu'' may be a very highly differentiated form of ], itself a highly differentiated form of ].<ref name="Basu">{{cite journal | vauthors = Basu A, Jagdish S, Iyengar KR, Basu D | title = Fetus in fetu or differentiated teratomas? | journal = Indian Journal of Pathology & Microbiology | volume = 49 | issue = 4 | pages = 563–565 | date = October 2006 | pmid = 17183856 | doi = }}</ref>


=== Parasitic twin hypothesis ===
*In June 1999, '''Sanju Bhagat''', a man from ], ], was rushed to a hospital due to difficulty ]. There, a surgical team removed from his bulging belly a ], a kind of ]. The report described that the surgical team found a living half-formed "creature" inside Mr. Bhagat's belly.<ref name=abc1>]'']</ref><ref name=kirch/>
⚫ {{Main|Parasitic twin}}
⚫ Fetus ''in fetu'' may be a ] ] growing within its ] ]. Very early in a ] twin pregnancy, in which both fetuses share a common placenta, one fetus wraps around and envelops the other. The enveloped twin becomes a ], in that its survival depends on the survival of the host twin, by drawing on the host twin's blood supply. The parasitic twin is ] (without a ]) and lacks some ]s, and as such is unable to survive on its own. As the host twin has to "feed" the enveloped twin from the nutrients received over a single umbilical cord, they usually die before birth.{{Citation needed|date=August 2008}}


⚫ == References ==
==Appearances in popular culture==
{{Reflist}}
* In ]'s novel '']'', a writer's past ''fetus in fetu'' teratoma, which had been found and removed in childhood, is linked to the later appearance of a murderous "evil twin" version of himself that takes on the pseudonymous identity the writer had used for a dark series of novels, and that he had just retired.
* In the '']'' episode "]" the main character has a parasitic twin who detaches from his "host" and kills people around the town.
*In season 2, episode 7 of the ABC television program ], a man believes he is pregnant; he turns out to have a teratoma.
*In the film '']'', Aunt Voula tells a story about "a lump on the back of neck" that contained "teeth, and a spinal column", probably a teratoma.
* The fate and identity of a fetus in fetu is a prominent plot line in the New Zealand drama series ]
*In the film '']'', Nikki describes a teratoma to Quincy.
*In '']'' (]) by ], Guzman's demons are caused by a teratoma.
* Pinoko, a character in the anime '']'', is actually a teratoma extracted by Black Jack from a patient. She was given a plastic exoskeleton, and came to live with Black Jack as his assistant after being rejected by her twin sister. Her name is an obvious reference to ], and she even sings a song about him in one episode.
* In ]'s multi-novel ], Stephen Maturin carries a preserved teratoma he had removed from a patient along with him as a prized possession.
* In the animated television series, '']'', durin one of Iqbal's speeches, he appears to be describing the lump removed from himself as having hair in teeth, and revealing it was his twin brother who had been buried inside him all those years.
*On ], Grace once expressed utter horror at a teratoma with little hair and teeth. She even said "When they poked it, it said 'Ow'."


⚫ == External links ==
⚫ ==References==
{{reflist}} {{Wiktionary}}
{{Commons category}}
*


{{Twin conditions}}
⚫ ==External links==
*], ], accessed ], ]]
*


⚫ ]
⚫ ]
] ]
⚫ ]
] ]
] ]
⚫ ]

]

Latest revision as of 22:51, 21 November 2024

Fetus-like mass within the body of its twin

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 from the previous image shows a fairly well developed fetus lying on its back, with rudimentary digits.
A computed tomography scan of the same patient's abdomen pre-operation 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 rare developmental abnormality in which a mass of tissue resembling a fetus forms inside the body of its twin. An early example of the phenomenon was described in 1808 by George William Young.

There are two hypotheses for the origin of a fetus in fetu. One hypothesis is that the mass begins as a normal fetus but becomes enveloped inside its twin. The other hypothesis is that the mass is a highly developed teratoma. Fetus in fetu is estimated to occur in 1 in 500,000 live births.

Classification as life

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.

Hypotheses of development

There are two main hypotheses about the development of fetus in fetu.

Teratoma hypothesis

Main article: Teratoma

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

Parasitic twin hypothesis

Main article: Parasitic twin

Fetus in fetu may be a parasitic twin fetus growing within its 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 its survival depends on the survival of the 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 unable to survive on its own. As the host twin has to "feed" the enveloped twin from the nutrients received over a single umbilical cord, they usually die before birth.

References

  1. Young GW (1808). "Case of a Fœtus found in the Abdomen of a Boy". Medico-Chirurgical Transactions. 1: 236–264. PMC 2128792. PMID 20895115.
  2. Chua JH, 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. doi:10.47102/annals-acadmedsg.V34N10p646. Archived from the original (PDF) on 2007-10-11.
  3. Grant P, Pearn JH (May 1969). "Foetus-in-foetu". The Medical Journal of Australia. 1 (20): 1016–1019. doi:10.5694/j.1326-5377.1969.tb49866.x. PMID 5815070. S2CID 209072187. — source not consulted; cited here following Hoeffel CC, Nguyen KQ, Phan HT, Truong NH, Nguyen TS, Tran TT, Fornes P (June 2000). "Fetus in fetu: a case report and literature review". Pediatrics. 105 (6): 1335–1344. doi:10.1542/peds.105.6.1335. PMID 10835078.
  4. Khalifa NM, Maximous DW, Abd-Elsayed AA (January 2008). "Fetus in fetu: a case report". Journal of Medical Case Reports. 2 (1). Jmedicalcasereports.com: 2. doi:10.1186/1752-1947-2-2. PMC 2253549. PMID 18186928.
  5. Basu A, Jagdish S, Iyengar KR, Basu D (October 2006). "Fetus in fetu or differentiated teratomas?". Indian Journal of Pathology & Microbiology. 49 (4): 563–565. PMID 17183856.

External links

Twin conditions
Zygosity
Monochorionic twins
Conjoined twins
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