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Fetus in fetu: A case report and review of the literature
Fetus in Fetu: A Case Report and Review of the Literature By Hock-Liew Eng, Jiin-Haur Chuang, Tze-Yu Lee, and Wei-Jen Chen Taiwan, Republic o f China 9 A cystic tumor was first found in the abdomen of a Taiwanese girl at the age of 9 months. The tumor gradually increased in size and caused no symptoms until the girl was 7 years of age, w h e n surgical removal was carried out. Pathological examination disclosed t w o "fetuses" within the fibrous sac, The pathogenesis of fetus in fetu and its differentiation from retroperitoneal teratoma are still controversial issues. Further w o r k needs to be done to elucidate w h e t h e r it is a natural progression of the twinning process to teratoma or the inclusion of a monozygotic diamniotic twin within the bearer, 9 1 9 8 9 by Grune & S t r a t t o n . Inc. I N D E X W O R D S : Fetus-in-fetu; teratoma.
~ETUS IN FETU, as quoted by Lewis, ~ is a term first coined by Meckel (circa 1800) to describe a rare condition in which a malformed parasitic twin was found inside the body of its partner, usually in the abdominal cavity. Its pathogenesis, diagnosis, and differentiation from retroperitoneal teratoma have long been the subjects of considerable controversy) In most reported cases, only one fetus was found. In this report, an example of this unusual entity with twin fetuses in the retroperitoneum is presented with unique clinical and pathologic features. Previously reported cases are briefly reviewed.
F
CASE REPORT A 7-year-old normally developed girl (body weight, 22 kg) who performs well in school is the firstborn child of her parents. Her two siblings are both in good health. There was no history of twinning or teratoma in the family. The mother's pregnancy had been normal and uneventful, and the girl had been delivered at full term. In the neonatal period, she was completely asymptomatic, with a normal growth and developmental pattern. At 9 months of age, her mother accidentally noticed a lump in the abdomen, but she did not pay much attention to it. At the age of 1 year 7 months, the girl was seen by a local medical doctor who noticed no increase in the size of the tumor. Although a laparotomy was performed, the tumor was not removed due to its close adhesion to the great vessels. About 2 years after the first operation, the family noted that the mass had progressively enlarged. The girl was admitted to the pediatric unit of Kaohsiung Medical Center, Chang Gung Memorial Hospital, where an examination of the abdomen showed a nontender fixed firm mass occupying almost the entire abdomen. No hepatosplenomegaly was
From the Departments of Pathology, Pediatric Surgery, and Radiology, Kaohsiung Medical Center, Chang Gung Memorial Hospital, Kaohsiung, Taiwan, Republic of China. Address reprint requests to Wei-Jen Chen, MD, Department of Pathology, Kaosiung Medical Center, Chang Gung Memorial Hospital, Kaohsiung, Taiwan, Republic of China. 9 1989 by Grune & Stratton, Inc. 0022-3468/89/2403-0017503.00/0 296
noted. Results of the laboratory examination, which included measurements of serum a-fetoprotein and B-HCG levels, were all within normal limits. The plain x-ray abdomen films showed bony structures within the retroperitoneal mass. An abdominal echogram showed a large tumor with low homogeneous echogenicity, and some foci of strong eehodensity in the upper portion. Computerized tomography (Fig 1) showed a huge retroperitoneal mass, measuring 20 x 17 x 11 cm, with components of cysts, bones, soft tissue, and fatty tissue. The mass extended from the subhepatic area of the hepatic caudate lobe to the anterior superior portion of the urinary bladder. The tumor had intimate contact with and displaced the kidneys, great vessels, intestinal loops, and liver. A clinical diagnosis of retroperitoneal teratoma was made. During surgery, a huge retroperitoneal mass was found occupying the entire right portion and almost all of the left portion of the abdomen. The small intestine, right colon, aorta, and inferior vena cava were displaced. Careful dissection was performed to separate the tumor from the adherent organs and vessels. The root of the tumor was found close to the base of the mesentery. It was removed in toto with the sac. The postoperative course was uneventful, and the patient was discharged on the fifth postoperative day. She has been perfectly well when observed in the follow-up clinic after 8 months.
RESULTS
Pathologic Findings. The tumor weighed roughly 500 g. It was found to have an intact grayish brown fibrous sac, about 0.5 cm in thickness. Upon opening, there were two feti-form structures attached separately to the fibrous sac, and bathing in a greenish turbid non-foul-odored fluid, with a suspended greasy milky white substance within the cystic spaces. No membranous separation was found between them (Fig 2). The fetuses measured 7 x 6 x 5.5 cm and 10 x 8.5 x 6 cm, respectively. Both were anencephalic with fetal greasy skin covering the entire bodies, and focally, were found to contain some fine black hairs. The smaller one was attached to the fibrous sac at its caudal end by a tubular structure. Two limb-like processes were present. One of them had two welldeveloped digits bearing well-formed nails. The roentgenography of the specimen (Fig 3) and subsequent dissection showed well-formed long bones with cartilaginous caps and marrow. Phalangeal bones with interphalangeal joints as well as metaphalangeal joints were noted in the fingers, which connected to a piece of scapula-shaped bone on the proximal end. However, no vertebral column was discernible. The larger fetus had a cephalic prominence and a ventral hilar depression. It was attached to the fibrous sac at its right lateral "chest" and left lower "foot" regions. Four limb-like structures were identified in Journal of PediatricSurgery, Vo124, No 3 (March), 1989: pp 296-299
FETUS IN FETU
297
Fig 1. Computerized t o mography shows a large cystic retroperitioneal mass consisting of t w o separate fetal struct u r e s o n d i f f e r e n t levels, with bony and soft tissue densities.
appropriate arrangement. The right "hand" had two digits with well-formed nails. The left hand had only one nail-bearing finger. The right lower limb showed two toes with nails. The left lower limb had seven toes with complete toenails present on four of them. A ventral protuberance was noted in the chest region, which, upon subsequent dissection and microscopic examination, was found to be composed mainly of marrow components. A roentgenographic examination showed well-developed long bones with cartilaginous caps. Interphalangeal joints were well demonstrated. No vertebral column was discernible.
With regard to histology, the fibrous sac was lined by keratinizing-stratified squamous epithelium with hair follicles and sweat glands. No chorionic villi or true placental tissue was found. The greater part of both fetuses consisted of fatty connective tissue. Highly differentiated blood and lymphatic vessels, a respiratory tract, brain tissue with neurons, nerve bundles with ganglion cells, skeletal muscle, and lymph nodes with germinal centers were found. Also, long bones with cartilage and a bone marrow with active hematopoiesis were conspicuous. No internal organs, except the attached tubular structure of the
Fig 2. T w o separate fetal masses are attached to the previously opened fibrous sac. The smaller fetus possesses t w o limblike s t r u c t u r e s , and the larger fetus possesses t w o upper and t w o lower limbs w i t h nails [arrows). S, fibrous sac; T, tubular structure attached to sac; L, limb; V, ventral protrusion.
Fig 3. Roentgenogrephy of the opened specimen shows t w o fetal masses consisting of long bones and phangeal bones, as well as a scapula-like structure, b, long bones; p, phalangeal bones; s, scapula-like structure.
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ENG ET AL
smaller fetus to the fibrous sac, were found. Microscopically, it was shown to be a colonic structure with fully developed mucosa, muscular coats, and serosa. Both fetuses were covered by skin with hair follicles, sebaceous glands, and sweat glands. DISCUSSION
Since Young 3 reported a case in 1809, only sporadic case reports of fetus in fetu have appeared in the literature. In her extensive review in 1956, Lord 4 noted 30 alleged cases reported prior to 1900, and 11 cases (including her own) from 1900 to 1956. Of the 11 cases, only four had unequivocal evidence of the condition. Subsequently, 19 additional case reports appeared in the literature. Fetus in fetu is discovered most often in early infancy as a retroperitoneal mass. Galatius-Jensen et al, 5 Highmore (as quoted by Lord4), and Knox and Webb 6 reported instances in children aged 17, 15, and 9, respectively. Of further interest, as quoted by Grosfeld et al, 7 a case of fetus in fetu was observed during an autopsy of an older man killed by an automobile accident. Janovski s described a Japanese boy in whom a 2.0-cm tumor was noted at the age of 3 months. The tumor had increased in size, but caused no symptoms until the child was five years of age. In the present case, the tumor was first noted when the girl was 9 months old. It progressively increased in size and remained in the abdomen for more than 6 years without causing symptoms. In most cases, the fetus in fetu was present intraabdominally and situated in the upper part of the retroperitoneal space. Examples of fetus in fetu in other sites are less common; other locations have been the cranial cavity,9 pelvis, ~~ scrotal sac, ~ sacrococcyx,~2 mesentery, ~3 and right iliac fossa. 6 The number of fetuses in fetu was usually one, however five were reported by Kimmel et al, 9 three by Lee, 1~and two by Gross and Clatworthy. ~4 In our case, two fetuses were found. The intraabdominal fetus in fetu is usually suspended by a pedicle within a complete sac, containing little fluid or sebaceous material, usually without definite vascular connection. Only two cases, one reported by Lee ~~ and one by Grant and Pearn, 15 showed definite vascular connection. The absence of an independent circulatory system could account for the subsequent fetal growth retardation. Only one case in the literature showed the presence of chorionic villi at the point where the sac attached to the abdominal wall. 13 Many theories have been advanced to elucidate the pathogenesis of fetus in fetu. ~'2'4't4 Previous investigators have hypothesized that fetus in fetu resulted from
a modified process of twinning, and have traced a natural progression from normal twins to conjoined symmetrical twins, through parasitic fetuses and fetal inclusion, and finally to teratoma. ~4'~6 On the other hand, in 1935, Willis 2 opposed the theory and stated that fetus in fetu most likely arises from inclusion of a monozygotic diamniotic twin within the bearer. He adopted the presence of a vertebral axis (indicating development through the stage of primitive streak) and an appropriate arrangement of other organs or limbs with respect to the vertebral axis as the criterion to distinguish fetus in fetu from highly differentiated teratoma. He regarded teratoma as a discordant congregation of pluripotential cells that demonstrates no vertebral segmentation or systemic organogenesis. Lacking a primary organizer, embryonic tissue composed of a teratoma cannot pass through an organized primitive streak stage, which endows the developing organism with its fundamental vertebral pattern. In addition, teratoma occurs in many extraretroperitoneal locations and has definite malignant potential. In contrast, the fetus in fetu is almost always benign in nature, and retroperitoneal in location. Willis' theory 2 is now generally accepted, and has been supported by genetic, cytogenetic, and serologic assessments. Studies on the eight blood group systems showed no difference between the host and the fetus. ~5't7 Chromosome studies of the fetus 7'~s'~7showed normal chromosomes, identical to those of the host. Lee 1~reported three fetusus found within a single sac removed from the abdomen of a 2-month-old infant, all of which had the same blood group (A) as their bearer. In two other cases (Brunkow, 1942; Lord, 1954), 4 intraabdominal gonads were present and corresponded histologically to the sex of the respective bearer. These studies tend to support the concept and virtually exclude dizygosity or aneuploidy, and indicated that the fetus in fetu was derived from the same zygote tissue as its host. However, a report of the concomitant presence of fetus in fetu and malignant teratoma suggests the validity of the earlier theory involving a natural progression of the twinning process to teratoma. is Because no definite vertebral column was identified in our case, we considered the probability of an extremely mature teratoma. Although the specimen in this case did not contain many body regions of a normal individual, it was thoroughly covered with skin and had well-developed limb-like processes on its surface, well-formed long bones with cartilage cap and marrow, and a colon with normally layered structures. Owing to its remarkable similarity to a fetus, we concluded that this case was one of fetus in fetu. As stated by Willis 2 and Lord, 4 we principally agree with
FETUS IN FETU
299
the theory that fetus in fetu is not a teratoma. However, some problems still exist concerning the cases that involved location in the cranial cavity, sacrococcygeal region, and scrotal sac. In addition, in cases with multiple fetal masses, not all of the fetal masses had
organized axial skeletons. Because of these uncertainties and the similar histologic findings, some investigations such as Lewis 1 and Warkany 19 have questioned whether a clear distinction can be made between the two conditions.
REFERENCES
1. Lewis PH: Foetus in foetu and the retroperitoneal teratoma.
Arch Dis Child 36:220-226, 1961 2. Willis RA: The structure of teratoma. J Pathol Bacteriol 40:1-36, 1935 3. Young GW: Case of a foetus found in the abdomen of a boy. Med Chir Trans 1:234, 1809 4. Lord JM: Intra-abdominal foetus in foetu. J Pathol Bacteriol 72:627-641, 1956 5. Galatius-Jensen F, Rah DH, Uhm IK, et ah Foetus in foetu. Br J Radiol 38:305, 1965 6. Knox AJS, Webb A J: The clinical features and treatment of fetus in fetu: Two case reports and a review of the literature. J Pediatr Surg 7:434, 1972 7. Grosfeld JL, Stepita DS, Nance WE, et al: Fetus in fetu: An unusual cause for abdominal mass in infancy. Ann Surg 180:80-84, 1974 8. Janovski NA: Fetus in fetu. J Pediatr 61:100-104, 1962 9. Kimmel DL, Moyer EK, Peale AP, et ah A cerebral tumor containing five human fetuses: A case of fetus in fetu. Anat Rec 106:141-158, 1950 I0. Lee EYC: Foetus in foetu. Arch Dis Child 40:689-693, 1965
11. Kakizoe T, Tahara M: Fetus in fetu located in the scrotal sac of a newborn infant: A case report. J Urol 506-508, 1972 12. Karasimbarao KL, Mitra SK, Pathak IC: Sacroooccygeal fetus-in-fetu. Indian Pediatr 21:820-822, 1984 13. Lamabadusariya SP, Atukrale AW, Soysa PE, et ah A case of fetus in fetu. Arch Dis Child 47:305-307, 1972 14. Gross RE, Clatworthy HW: Twin fetuses in fetu. J Pediatr 38:502-508, 1951 15. Grant P, Pearn JH: Foetus in foetu. Med J Aust 1:1016-1019, 1969 16. Potter EL: Pathology of the Fetus and the Newborn (ed 2). Chicago, Year Book Medical, 1962, pp 183-187 17. Boyce M J, Lockyer JW, Wood CBS: Foetus in foetu: Serological assessment of monozygotic origin by automated analysis. J Clin Pathol 25:793-798, 1972 18. Du Plessis JPG, Winship WS, Kirstein JDL: Fetus in fetu and teratoma: A case report and review. S Aft Med J 48:2119-2122, 1974 19. Warkany J: Congenital malformations. Chicago, Year Book Medical, 1971, pp 1244-1245
~ETUS IN FETU, as quoted by Lewis, ~ is a term first coined by Meckel (circa 1800) to describe a rare condition in which a malformed parasitic twin was found inside the body of its partner, usually in the abdominal cavity. Its pathogenesis, diagnosis, and differentiation from retroperitoneal teratoma have long been the subjects of considerable controversy) In most reported cases, only one fetus was found. In this report, an example of this unusual entity with twin fetuses in the retroperitoneum is presented with unique clinical and pathologic features. Previously reported cases are briefly reviewed.
F
CASE REPORT A 7-year-old normally developed girl (body weight, 22 kg) who performs well in school is the firstborn child of her parents. Her two siblings are both in good health. There was no history of twinning or teratoma in the family. The mother's pregnancy had been normal and uneventful, and the girl had been delivered at full term. In the neonatal period, she was completely asymptomatic, with a normal growth and developmental pattern. At 9 months of age, her mother accidentally noticed a lump in the abdomen, but she did not pay much attention to it. At the age of 1 year 7 months, the girl was seen by a local medical doctor who noticed no increase in the size of the tumor. Although a laparotomy was performed, the tumor was not removed due to its close adhesion to the great vessels. About 2 years after the first operation, the family noted that the mass had progressively enlarged. The girl was admitted to the pediatric unit of Kaohsiung Medical Center, Chang Gung Memorial Hospital, where an examination of the abdomen showed a nontender fixed firm mass occupying almost the entire abdomen. No hepatosplenomegaly was
From the Departments of Pathology, Pediatric Surgery, and Radiology, Kaohsiung Medical Center, Chang Gung Memorial Hospital, Kaohsiung, Taiwan, Republic of China. Address reprint requests to Wei-Jen Chen, MD, Department of Pathology, Kaosiung Medical Center, Chang Gung Memorial Hospital, Kaohsiung, Taiwan, Republic of China. 9 1989 by Grune & Stratton, Inc. 0022-3468/89/2403-0017503.00/0 296
noted. Results of the laboratory examination, which included measurements of serum a-fetoprotein and B-HCG levels, were all within normal limits. The plain x-ray abdomen films showed bony structures within the retroperitoneal mass. An abdominal echogram showed a large tumor with low homogeneous echogenicity, and some foci of strong eehodensity in the upper portion. Computerized tomography (Fig 1) showed a huge retroperitoneal mass, measuring 20 x 17 x 11 cm, with components of cysts, bones, soft tissue, and fatty tissue. The mass extended from the subhepatic area of the hepatic caudate lobe to the anterior superior portion of the urinary bladder. The tumor had intimate contact with and displaced the kidneys, great vessels, intestinal loops, and liver. A clinical diagnosis of retroperitoneal teratoma was made. During surgery, a huge retroperitoneal mass was found occupying the entire right portion and almost all of the left portion of the abdomen. The small intestine, right colon, aorta, and inferior vena cava were displaced. Careful dissection was performed to separate the tumor from the adherent organs and vessels. The root of the tumor was found close to the base of the mesentery. It was removed in toto with the sac. The postoperative course was uneventful, and the patient was discharged on the fifth postoperative day. She has been perfectly well when observed in the follow-up clinic after 8 months.
RESULTS
Pathologic Findings. The tumor weighed roughly 500 g. It was found to have an intact grayish brown fibrous sac, about 0.5 cm in thickness. Upon opening, there were two feti-form structures attached separately to the fibrous sac, and bathing in a greenish turbid non-foul-odored fluid, with a suspended greasy milky white substance within the cystic spaces. No membranous separation was found between them (Fig 2). The fetuses measured 7 x 6 x 5.5 cm and 10 x 8.5 x 6 cm, respectively. Both were anencephalic with fetal greasy skin covering the entire bodies, and focally, were found to contain some fine black hairs. The smaller one was attached to the fibrous sac at its caudal end by a tubular structure. Two limb-like processes were present. One of them had two welldeveloped digits bearing well-formed nails. The roentgenography of the specimen (Fig 3) and subsequent dissection showed well-formed long bones with cartilaginous caps and marrow. Phalangeal bones with interphalangeal joints as well as metaphalangeal joints were noted in the fingers, which connected to a piece of scapula-shaped bone on the proximal end. However, no vertebral column was discernible. The larger fetus had a cephalic prominence and a ventral hilar depression. It was attached to the fibrous sac at its right lateral "chest" and left lower "foot" regions. Four limb-like structures were identified in Journal of PediatricSurgery, Vo124, No 3 (March), 1989: pp 296-299
FETUS IN FETU
297
Fig 1. Computerized t o mography shows a large cystic retroperitioneal mass consisting of t w o separate fetal struct u r e s o n d i f f e r e n t levels, with bony and soft tissue densities.
appropriate arrangement. The right "hand" had two digits with well-formed nails. The left hand had only one nail-bearing finger. The right lower limb showed two toes with nails. The left lower limb had seven toes with complete toenails present on four of them. A ventral protuberance was noted in the chest region, which, upon subsequent dissection and microscopic examination, was found to be composed mainly of marrow components. A roentgenographic examination showed well-developed long bones with cartilaginous caps. Interphalangeal joints were well demonstrated. No vertebral column was discernible.
With regard to histology, the fibrous sac was lined by keratinizing-stratified squamous epithelium with hair follicles and sweat glands. No chorionic villi or true placental tissue was found. The greater part of both fetuses consisted of fatty connective tissue. Highly differentiated blood and lymphatic vessels, a respiratory tract, brain tissue with neurons, nerve bundles with ganglion cells, skeletal muscle, and lymph nodes with germinal centers were found. Also, long bones with cartilage and a bone marrow with active hematopoiesis were conspicuous. No internal organs, except the attached tubular structure of the
Fig 2. T w o separate fetal masses are attached to the previously opened fibrous sac. The smaller fetus possesses t w o limblike s t r u c t u r e s , and the larger fetus possesses t w o upper and t w o lower limbs w i t h nails [arrows). S, fibrous sac; T, tubular structure attached to sac; L, limb; V, ventral protrusion.
Fig 3. Roentgenogrephy of the opened specimen shows t w o fetal masses consisting of long bones and phangeal bones, as well as a scapula-like structure, b, long bones; p, phalangeal bones; s, scapula-like structure.
298
ENG ET AL
smaller fetus to the fibrous sac, were found. Microscopically, it was shown to be a colonic structure with fully developed mucosa, muscular coats, and serosa. Both fetuses were covered by skin with hair follicles, sebaceous glands, and sweat glands. DISCUSSION
Since Young 3 reported a case in 1809, only sporadic case reports of fetus in fetu have appeared in the literature. In her extensive review in 1956, Lord 4 noted 30 alleged cases reported prior to 1900, and 11 cases (including her own) from 1900 to 1956. Of the 11 cases, only four had unequivocal evidence of the condition. Subsequently, 19 additional case reports appeared in the literature. Fetus in fetu is discovered most often in early infancy as a retroperitoneal mass. Galatius-Jensen et al, 5 Highmore (as quoted by Lord4), and Knox and Webb 6 reported instances in children aged 17, 15, and 9, respectively. Of further interest, as quoted by Grosfeld et al, 7 a case of fetus in fetu was observed during an autopsy of an older man killed by an automobile accident. Janovski s described a Japanese boy in whom a 2.0-cm tumor was noted at the age of 3 months. The tumor had increased in size, but caused no symptoms until the child was five years of age. In the present case, the tumor was first noted when the girl was 9 months old. It progressively increased in size and remained in the abdomen for more than 6 years without causing symptoms. In most cases, the fetus in fetu was present intraabdominally and situated in the upper part of the retroperitoneal space. Examples of fetus in fetu in other sites are less common; other locations have been the cranial cavity,9 pelvis, ~~ scrotal sac, ~ sacrococcyx,~2 mesentery, ~3 and right iliac fossa. 6 The number of fetuses in fetu was usually one, however five were reported by Kimmel et al, 9 three by Lee, 1~and two by Gross and Clatworthy. ~4 In our case, two fetuses were found. The intraabdominal fetus in fetu is usually suspended by a pedicle within a complete sac, containing little fluid or sebaceous material, usually without definite vascular connection. Only two cases, one reported by Lee ~~ and one by Grant and Pearn, 15 showed definite vascular connection. The absence of an independent circulatory system could account for the subsequent fetal growth retardation. Only one case in the literature showed the presence of chorionic villi at the point where the sac attached to the abdominal wall. 13 Many theories have been advanced to elucidate the pathogenesis of fetus in fetu. ~'2'4't4 Previous investigators have hypothesized that fetus in fetu resulted from
a modified process of twinning, and have traced a natural progression from normal twins to conjoined symmetrical twins, through parasitic fetuses and fetal inclusion, and finally to teratoma. ~4'~6 On the other hand, in 1935, Willis 2 opposed the theory and stated that fetus in fetu most likely arises from inclusion of a monozygotic diamniotic twin within the bearer. He adopted the presence of a vertebral axis (indicating development through the stage of primitive streak) and an appropriate arrangement of other organs or limbs with respect to the vertebral axis as the criterion to distinguish fetus in fetu from highly differentiated teratoma. He regarded teratoma as a discordant congregation of pluripotential cells that demonstrates no vertebral segmentation or systemic organogenesis. Lacking a primary organizer, embryonic tissue composed of a teratoma cannot pass through an organized primitive streak stage, which endows the developing organism with its fundamental vertebral pattern. In addition, teratoma occurs in many extraretroperitoneal locations and has definite malignant potential. In contrast, the fetus in fetu is almost always benign in nature, and retroperitoneal in location. Willis' theory 2 is now generally accepted, and has been supported by genetic, cytogenetic, and serologic assessments. Studies on the eight blood group systems showed no difference between the host and the fetus. ~5't7 Chromosome studies of the fetus 7'~s'~7showed normal chromosomes, identical to those of the host. Lee 1~reported three fetusus found within a single sac removed from the abdomen of a 2-month-old infant, all of which had the same blood group (A) as their bearer. In two other cases (Brunkow, 1942; Lord, 1954), 4 intraabdominal gonads were present and corresponded histologically to the sex of the respective bearer. These studies tend to support the concept and virtually exclude dizygosity or aneuploidy, and indicated that the fetus in fetu was derived from the same zygote tissue as its host. However, a report of the concomitant presence of fetus in fetu and malignant teratoma suggests the validity of the earlier theory involving a natural progression of the twinning process to teratoma. is Because no definite vertebral column was identified in our case, we considered the probability of an extremely mature teratoma. Although the specimen in this case did not contain many body regions of a normal individual, it was thoroughly covered with skin and had well-developed limb-like processes on its surface, well-formed long bones with cartilage cap and marrow, and a colon with normally layered structures. Owing to its remarkable similarity to a fetus, we concluded that this case was one of fetus in fetu. As stated by Willis 2 and Lord, 4 we principally agree with
FETUS IN FETU
299
the theory that fetus in fetu is not a teratoma. However, some problems still exist concerning the cases that involved location in the cranial cavity, sacrococcygeal region, and scrotal sac. In addition, in cases with multiple fetal masses, not all of the fetal masses had
organized axial skeletons. Because of these uncertainties and the similar histologic findings, some investigations such as Lewis 1 and Warkany 19 have questioned whether a clear distinction can be made between the two conditions.
REFERENCES
1. Lewis PH: Foetus in foetu and the retroperitoneal teratoma.
Arch Dis Child 36:220-226, 1961 2. Willis RA: The structure of teratoma. J Pathol Bacteriol 40:1-36, 1935 3. Young GW: Case of a foetus found in the abdomen of a boy. Med Chir Trans 1:234, 1809 4. Lord JM: Intra-abdominal foetus in foetu. J Pathol Bacteriol 72:627-641, 1956 5. Galatius-Jensen F, Rah DH, Uhm IK, et ah Foetus in foetu. Br J Radiol 38:305, 1965 6. Knox AJS, Webb A J: The clinical features and treatment of fetus in fetu: Two case reports and a review of the literature. J Pediatr Surg 7:434, 1972 7. Grosfeld JL, Stepita DS, Nance WE, et al: Fetus in fetu: An unusual cause for abdominal mass in infancy. Ann Surg 180:80-84, 1974 8. Janovski NA: Fetus in fetu. J Pediatr 61:100-104, 1962 9. Kimmel DL, Moyer EK, Peale AP, et ah A cerebral tumor containing five human fetuses: A case of fetus in fetu. Anat Rec 106:141-158, 1950 I0. Lee EYC: Foetus in foetu. Arch Dis Child 40:689-693, 1965
11. Kakizoe T, Tahara M: Fetus in fetu located in the scrotal sac of a newborn infant: A case report. J Urol 506-508, 1972 12. Karasimbarao KL, Mitra SK, Pathak IC: Sacroooccygeal fetus-in-fetu. Indian Pediatr 21:820-822, 1984 13. Lamabadusariya SP, Atukrale AW, Soysa PE, et ah A case of fetus in fetu. Arch Dis Child 47:305-307, 1972 14. Gross RE, Clatworthy HW: Twin fetuses in fetu. J Pediatr 38:502-508, 1951 15. Grant P, Pearn JH: Foetus in foetu. Med J Aust 1:1016-1019, 1969 16. Potter EL: Pathology of the Fetus and the Newborn (ed 2). Chicago, Year Book Medical, 1962, pp 183-187 17. Boyce M J, Lockyer JW, Wood CBS: Foetus in foetu: Serological assessment of monozygotic origin by automated analysis. J Clin Pathol 25:793-798, 1972 18. Du Plessis JPG, Winship WS, Kirstein JDL: Fetus in fetu and teratoma: A case report and review. S Aft Med J 48:2119-2122, 1974 19. Warkany J: Congenital malformations. Chicago, Year Book Medical, 1971, pp 1244-1245