Pediutr Surg tnt (2009) 25:289-292

DOI 10. I 007is003s3-009-232S-S

Fetus in fetu: two case reports and review of literature

Jamir D. Arlikar Shivaji B. I\{anc .

Nitin P. Dhende . Yogendra Sanghavi.Arvind G. Valand . Pradip R. Butale

Accepted: l6 January 2009/Published online: 3l January 2009O Springer-Verlag 2009

Abstract Fetus in fetu is a rare disorder. Its enrbryopa-thogensis and differentiation from teratoma has not beenwell established. It is a parasitic twin oi a dianrnioticnlonozygotic twin. Here \\,e report, two cases of fetus infetu with review of literature. In cas:'report 1, a 2-year-oldboy was referred for asymrtonratic Iump in abdomensince birth. X-ray showed tlre mass in the abdomen withsorne calcification and fluid inside. CT scan reported aheterogenous .mass in the retroperitoneum with bonymalformation. CT showed presence of three vertebrae in it.Atter surgically excising the mass and opening the sac itshowed presence o[ trunk and two limbs *,ith one of thelimbs having a nail. Histopathology showed presence of GItract. In case report 2, 4 rnonth female was found to havelump in the abdomen by housemaid while bathing. X-rayshowed a soft tissue shadow while ultrasonographyrevealed cysric mass arising lrom right kidney. CT sug-gested cystic nrass with calcification not arising fromkidney. During exploration whole mass was excised andthere rvas frank ietus inside ir. Histopathology confirmedpresence of four vertebral bodies rvith germ Iayers.Although fetus in fetu is rare condition, correct diagnosisusing ima_ein_e can be ntade before surgery. Completeexcision is curative.

J. D. Arlikar (8) . S. B. Mane . N. P. Dhende . y. SanghaviA. C. Vuland . P. R. BuraleCrant Medical College, Munrbai, Indiae-nrail : jarnirarl ikar@ gmail.corn

J. D. Arlikar . S. B. Mane . N. P. Dhende . Y. Sanghavi .

A. C. Valand . P R. ButaleSir JJ Croup of Hospirals, Mumbai, India

Iutroduction

Fetus in fetu is a rare condition rvith less than 200 cascrs

reponed in the world to the best of our knowledge. Meckelfirst described this condition. It was Willis who coined thc.

term Fetus in fetu. In this condition, malformed par.asitir:

twin is found inside the body of irs partrler usually theabdominal cavity. Though the most common site is theabdominal cavity, it has also been found in posteriormediastinum, neck, and in sacrococcygeal region. Com-monest site is in the retroperitoneum (807o). Majority ofcases occur in infancy, but can be detected at any age.

Case report 1

A 2-year-old boy had history of lump in abdomen sincebirth. Initiallv it was small, but gradually increased toattain the present size o[ 20 x 20 cm. The child had noother symptoms. The mass had variegated consisrencl,,relatively fixed, and non tender. Radiograph showed cal-cified mass pushing the intestine. USG revealed a large,hyperechoic, and heterogeneous mass in the abdomen. CTsuggested a mass in the retroperitoneum with calcifiedtissue and presence of vertebrae inside. So, a differentialdiagnosis of teratoma and fetus in fetu was considered. Inexploratory laparotomy there was a mass in the retroperi-toneum in close proximity rvith the intestine, pancreas, ancJ

stomach. [t was almost 20 x 18 cm in size, partly cysticand partly bony. There was no feeding vesse, to it. It had acovering around it, which accidently ruptured releasingserous fluid. In toto excision o[ mass was done. Afteropening the sac it had a limb-like srrucrure along with nailu,ith a poorly l'ormed head. Also it was easy to nrake outthe back and parr suggesrive of spine. Radiology ol rhe

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290 Pedietr Surg lnt (2009) 25:2S9-291

Fig. I Casevertebrae

l-CT scan showing mass in the abdomen with three

Fig. 2 Case I---+ncapsulated mass in close relarion with the intestine

mass confirmed the presence of bony limbs and two ver-tebrae. Histopathology also showed the presence GI organsinside the mass. The patient rvas discharged withoutcomplications and is being followed up since the lastI I months without any recurrence on ultrasonography(Figs. I , 2,3).

Ca-se report 2

A 4-month-old lemale was diagnosed with a lump in theabdomen. She had no orher complaints. Abdominalexamination showed a mass in the righr hypochondrium,

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Fig. 3 Case l-after removing the capsule, back and limbs with nail

soft and cystic in consistency. X-ray was suggestive of sofr

tissue shadow with no calcification. Ultrasonography olabdomen showed cystic mass arising from kidney. But C'l'scan of abdomen revealed that the mass was separate frontthe kidney and filled with cystic fluid without any calcifi-cation. So with diagnosis of teratoma and keeping in miutlpossibility of fetus, in fetu exploratory laparotomy rvas

done. It was retroperitoneal mass in close relation withsmall bowel and right kidney. The mass was exciscdcompletely. There was no feeding vessel to it. Once ourr:rcyst wall was opened there were fetal parts. We coulri

-identify fetal skull with limbs. Histopathology confirmedthe presence of four vertebrae with three germ layers in themass. The patient was discharged without any complica-tions and is following with us for last 24 months withourany recurrence (Figs. 4,5,6).

Discussion

Fetus in fetu is very rare condition. The overall incidence isI in 5,00,000 live births []. It is the malformed monozv-gotic diamniotic twin which is found inside the body of a

Iiving child or sonletimes in an adult. It is thought to resulrfrom unequal division of totipotent inner cell mass ol thedeveloping blastocyst which results in small cell masswithin a maturing sister embryo. The ultimate result isvestigial remnant of a dianrniotic monochorionic twin thatis located within the body of an orherwise normallydeveloped twin [2]. Mostly, it is a single parasitic twin, butcan range from 2 to 5. The organs present can be vertebraicolumn, limbs, central nervous system, gastrointestinaltract, vessels, and genitourinary tract. Classically they are

anencephalic. An unusual leature of our first case was thepresence of limb rvith nail and the presence of well

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developed intestine and the absence of other u,etl-difler-entiated organs.

Presentation is usualll' before age of l8 nronths, but the

oldest reported case is of47-year-old adult. Thakral et al. [3]reported equaI male and female predisposition but Patankar

et al. and Federici et al. [4] noted a 2: I male predominance.

The comrrron presentation is rnass [3] nrost commonly in the

abdomen, almost 807o in retroperitoneum [5] but sometimes

can present as lllass in skull [G-9] in 87o, sacrum [0-la] in

87o, scrotum [5] in l7o, ntouth [16] in l7o, posteriormediastinum [ 17] in lVo, liver [l 8] one report. One of ourcases had presentation at the age of4 rnonths and other at

the age of 24 months though he had abdominal lump sincebirth. Symptoms of fetus in fetu relate mainly to its nrass

effect and include abdominal distension, feeding difficulty,pressure effects on renal system, and dyspnoea [4, 19, 20].Preoperative diagnosis is now possible with advent of CT.Plain abdominal X-ray may be helpful in diagnosis, rvithhalf of them showing vertebral column and axial skeleton.Though rare anomaly fetus in fetu can be identified in pre-

operati ve period radiologically [9, 2l -23]. Mosr commonll,they are found in upper retroperitoneum; both of our cases

had mass in the reti.peritoneum.Intra-abdt minal fetus is usually contained in a complete

sac, without any major vascular connections to the host.Predominant blood supply appears to be derived from rheplexus where the fetus in fetu and the sac are attached tothe abdominal wall [24], as in our case. Complere excisionof the mass is curative. Complete excision of surroundingmembrane should ensure definirive cure 119, 24-261.Hopkins et al. [19] reported a malignant recurrence fol-lowing resection of fetus in fetu. This was presumablycaused by transformation of adherent membranes remain-ing at surgical sites. One should not try to deflate rhe

capsule or membrane. Il possible, the membrane should beremoved intact. Cases of reported fetus in fetu weighedbetween 13 g {27) and 2,000 C [28].

Pathological controversy arises during differentiation offetus in fetu from a mature or well organized teratoma.According to Willis (1935), presence of, axial skeleton withvertebral axis with an appropriate arrangement of otherlimbs and organs, with respect to axis goes more in favor offetus in fetu as it indicates abortive attempt alter the stageof primitive streak formation [2]. In one of our cases, as

described in literature, the vertebral column was detectedby pathologist. So it was in accordance with Willis theory.It was radiolucenr on radiography as it was less calcified

[29]. Occasional bases have been reported where no spinalcolumn rvas found on radiography [2]. However, review ofliterature showed that in about 9olo o[ cases of fetus in fetu,there rvas no vertebral column, even on pathologic exam-ination [30]. This has led ro anorher definirion proposedby Gctzalez--Crussi [30]:"Ferus in letu is applied to any

structure in s'hich the fetal lornr is in a very high devel-

opnrent of organogenesis and Io the presence of vertebral

axis" [30]. Our first case falls in the category of f,etus infetu by definition proposed by Gonzalez-Crussi. On [he

other hand, teratoma is an accumulation of pluripotentialcells in which there is neither organogenesis nor vertebral

segmentation [3 l]. Another important aspect oi fetus infetu is that they never become malignant whereas teraton'la

is known to become malignant [25]. Some supporters ofteratoma theory have suggested that the fetus in fetu mass

represents a rvell-differentiated, highly organized teratouta

[24]. So it remains controversial whether fetus in fetu is a

distinct entity or represents a highly organized teratonla.Du Plessis et al. [32] reported an interesting patient withboth well formed fetus in fetu and a malignant teratorlra,

stating that that was "a potential triplet situation gone-

awry, resulting in the host, his parasitic twin and teratoma

Fig. 4 Case 2--CT scan depicting mass in the abdomen u'ithout anycalcification

Fig. 5 Case 2-intraoperative showing capsulated mass in proximitywith the intestine

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Fig.6 Case 2-frank fetal .specimen, histopathology showed pres_ence of four vertebrae and three germ cell lry.r,

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arising from a third embryo which may have escaped theinfluence of its primary organizer". occasional cases havebeen reported in literature where there are no vertebralbodies as it indicates dysplastic vertebral bodies whichwere not identified.

Conclusion

Fetus in fetu is a rare and interesting entit)/ that typicallypresents as an abdominal mass in infancy or early child-hood which can be diagnosed in the preoperative period.Complete excision of mass is curative and confirmatory.

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