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KumarA, etal. BMJ Case Rep 2019;12:e230835. doi:10.1136/bcr-2019-230835
Case report
Fetus in fetu in an adultwoman
Anil Kumar,
1
Shiv Shankar Paswan,
2
Bindey Kumar,
3
Prem Kumar
4
Rare disease
To cite: KumarA, PaswanSS,
KumarB, etal. BMJ Case
Rep 2019;12:e230835.
doi:10.1136/bcr-2019-
230835
1
General Surgery (Trauma),
All India Institute of Medical
Sciences, Patna, Bihar, India
2
Trauma and Emergency, All
India Institute of Medical
Sciences, Bhubaneswar, Odisha,
India
3
Pediatric Surgery, All India
Institute of Medical Sciences,
Patna, Bihar, India
4
Radiodiagnosis, All India
Institute of Medical Sciences,
Patna, Bihar, India
Correspondence to
DrAnil Kumar,
dranil4@ gmail. com
Accepted 24 July 2019
© BMJ Publishing Group
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permitted under CC BY-NC. No
commercial re-use. See rights
and permissions. Published
by BMJ.
SUMMARY
Fetus in fetu (FIF) is an extremely rare condition in
which malformed fetus is found most commonly
in the retroperitoneum of living twin. It occurs in
about 1 in 500 000 live births and less than 200
cases have been reported in medical literature. We
report FIF in a 17-year-old woman unlike other
cases which were usually detected in early age and
in male gender. This is the eighth case of adult FIF
and the first case of FIF in adult woman worldwide.
Preoperative diagnosis of FIF on CT was made and
planned for exploratory laparotomy. The excised
malformed fetus in a sac was proven as FIF on the
basis of histopathological examination. In view to
avoid such late presentation, early detection of FIF
with radiological imaging in clinically suspected
case is recommended. Surgical excision is the ideal
treatment even teratoma is the differential diagnosis.
BACKGROUND
Fetus in fetu (FIF) is a rare developmental abnor-
mality in which a malformed fetus is found within
the body of other twin. It was first described by
Johann Friedrich Meckel in the late 18th century.
Majority of cases have been described in neonates
and children and only seven cases have been
reported after the age of 15 years (table 1). The first
reported case of FIF in an adult man, whose age was
47 years, is by Dagradi et al
1
All reported cases of
adult FIF were in male gender. We aim to report
this case since to the best of our knowledge this case
is the first case of FIF in a female gender of 17 years
age and reviewing the literature.
CASE PRESENTATION
A 17-year-old woman presented with abdominal
lump for 5 years, which was gradually increasing in
size. It was associated with pain in abdomen which
was on and off in nature. She was also complaining
of early satiety but there was no history of signif-
icant weight loss. There was no history of altered
bowel habits and urinary symptoms. Her menstrual
history was within the normal limits. There was no
history of twin birth or teratoma in the family. Her
general, physical and systemic examinations were
within the normal limits. On abdominal examina-
tion, there was a mass involving the whole of the
abdomen (figure 1). This abdominal lump was firm
to hard in consistency, its surface was irregular,
margins were ill-defined and it was not moving with
respiration. With these clinical information except
to say abdominal tumour, it was not possible to
conclude a final diagnosis.
INVESTIGATIONS
On evaluation, beta-human chorionic gonad-
otropin (β-HCG), alpha feto protein and
routine blood investigations were found within
the normal limits. An abdominal contrast-en-
hanced computed tomography (CECT) scan
showed a well-defined mass that measured
approximately 25×23×15 cm, extending
from epigastrium to upper pelvis (figure 2). It
was showing fat density areas, soft tissue and
multiple calcified density components of various
sizes and shapes resembling the shape of verte-
brae, ribs and long bones. This mass was causing
displacement and compression of adjacent
abdominal viscera.
DIFFERENTIAL DIAGNOSIS
On the basis of clinical findings (slow growing
abdominal lump with firm to hard consistency,
irregular surface and ill-defined margins) and CECT
findings (well-defined mass with fat density areas
and multiple calcified density resembling shape of
vertebrae, ribs and long bones), a clinical diagnosis
of FIF was made preoperatively.
TREATMENT
On exploration, there was a large retroperitoneal
encapsulated mass, extending from the under
surface of the liver reaching up to the pelvic rim
(figure 3). It was grossly displacing intra-abdom-
inal viscera however no invasion was noted. The
contents of the tumour consisted of hairs, mature
bones and other body parts (figure 4). The contents
were removed in toto and a part of cyst wall which
was densely adherent to the mesenteric vessels was
left behind in order to prevent devascularization of
gastrointestinal tract. The remaining cyst wall was
cauterised. On macroscopic examination, the mass
measured 30×16×10 cm and was composed of
hairy cheesy material, multiple teeth and structures
Table 1 Fetus in fetu in adult cases published in
between 1999 and 2016
Adult
FIF cases
reported by
(authors)
Year of
reporting
Age of
patient at
the time of
diagnosis Sex Location
Shrivastava 1999 27 Years Male Retroperitoneum(RP)
Patankar 2000 16 Years Male RP
Awasthi 2001 30 Years Male RP
Masad 2001 27 Years Male RP
Lee 2005 39 Years Male Intraperitoneal
Sharma 2007 36 Years Male RP
Daga 2009 20 Years Male RP
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KumarA, etal. BMJ Case Rep 2019;12:e230835. doi:10.1136/bcr-2019-230835
Rare disease
resembling limb buds. On cutting section, it showed fatty, carti-
laginous and bony areas along with another cystic area of size
8×7 cm. Microscopically, there was an admixture of different
elements including neural, intestinal, cartilaginous and bone
along with skin adnexal structures and adipose tissue. However,
no immature elements were seen. A final diagnosis of FIF was
given on the basis of histopathological findings.
OUTCOME AND FOLLOW-UP
Her postoperative period was uneventful. She has now been
on our follow-up for the last 24 months with normal level of
β-HCG and is doing well.
DISCUSSION
FIF is a condition, commonly occurs in retroperitoneal space
(80%).
2
Others rare sites like sacrococcygeal region, intracra-
nial, thorax, pelvis, scrotum, back and oral cavity have also
been described in the literature.
3–5
There are two theories for
the development of FIF. One is parasitic twin theory in which
parasitic malformed fetus formed inside the body of its host twin
and share common blood supply. The parasitic twin is anen-
cephalic with lack of many internal organs and it usually dies
before birth.
6
The other theory is that FIF is a highly differen-
tiated form of teratoma.
7
However, Willis (1953) emphasised
the definition of FIF as a mass containing a vertebral axis along
with other organs or limbs.
8
Recently, many cases have reported
as FIF without the presence of vertebral column but features of
advanced stage of organogenesis.
9
Majority of the reported cases of FIF are found in infancy
and neonatal age group unlike our case.
10–14
Excluding
the present case, only seven adult cases of FIF have been
reported in the literature.
15
Among adult cases of FIF, the
oldest and the youngest case was 47 years and 20 years
old respectively, while the age of present case was only 17
years.
1 16
In older age, although diagnosis is more in favour
of retroperitoneal teratoma the possibility of FIF cannot be
ruled out. Moreover it is in fact very difficult to differen-
tiate these two conditions. Willis in 1953 set the criteria to
differentiate these two conditions that FIF contains a verte-
bral axis with organs and limbs arranged around it, whereas
teratoma is an accumulation of pluripotent cells in which
there is neither organogenesis nor vertebral segmentation.
17
The preoperative diagnosis of FIF can be made on radio-
logical findings.
18
Plain abdominal X-rays may be helpful in
diagnosis of a vertebral column and axial skelton. A CECT
would easily pick the presence of axial skelton and fatty
tissue around it as in our case. Complete excision of FIF
with its all surrounding membrane is the treatment of choice
because of the possibility of malignant transformation.
19
The
possibility of malignant transformation is more found if the
Figure 1 Showing abdominal lump with ill-defined margin.
Figure 2 Abdominal contrast-enhanced computed tomography
showing 25×23×15 cm mass with multiple calcified densities
compressing the adjacent abdominal viscera.
Figure 3 Showing encapsulated mass extending from the under
surface of the liver reaching up to the pelvic rim.
Figure 4 Specimen consists of hairs, mature bones and other body
parts.
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KumarA, etal. BMJ Case Rep 2019;12:e230835. doi:10.1136/bcr-2019-230835
Rare disease
tissue of FIF remains left after surgery.
20
Although the prog-
nosis for FIF is more favourable than for cystic teratoma,
the presence of immature elements mandates close clinical,
radiological and serological follow-up to detect recurrence.
This case will be follow-up at every year in view to detect
malignancy as some adherent tissue was left during surgery.
Patient’s perspective
I was much worried about my abdominal lump, after operation
I am feeling very well and my abdomen is now flat and my
parents are also very happy. Thanks to all operating doctors.
Learning points
► Fetus in fetu (FIF) is a rare condition usually occurs in infancy
and child age group.
► FIF in a 17-year-old woman is an extremely rare condition.
► This case is the eighth case of adult FIF and the first case of
FIF in adult woman worldwide.
► Among all reported cases of adult FIF until, this case
represents the largest size of FIF measured 36×16×10 cm.
Contributors Manuscript writing, editing and design: AK; concept and operating
the patient: SSP; review of literature and radiological review of CT film: PK; review of
the manuscript and literature search: BK.
Funding The authors have not declared a specific grant for this research from any
funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.
Open access This is an open access article distributed in accordance with the
Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which
permits others to distribute, remix, adapt, build upon this work non-commercially,
and license their derivative works on different terms, provided the original work
is properly cited and the use is non-commercial. See: http:// creativecommons. org/
licenses/ by- nc/ 4. 0/
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