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Fetus-in-Fetu
Fetus-in-Fetu Daniel Kaufman, MD, Litong Du, MD, Francesca T Velcek, MD, FACS, Antonio E Alfonso, MD, FACS Long Island College Hospital, State University of New York, Downstate Medical Center, Brooklyn, NY
A
B
C
D
A 2-year-old boy presented with a 5-month history of postprandial abdominal pain and bloody stools. He had previously undergone laparoscopic exploration for an undescended right testicle. Physical examination showed a grapefruit-sized, firm, nontender, solid mass in the right lower quadrant, without erythema or discoloration of the overlying skin. Laboratory tests and chest x-ray were normal. CT scan and MRI of the abdomen showed a large, complex, soft-tissue mass with bony elements (arrows in A and B). At laparotomy a retroperitoneal mass, 12 ⫻ 15 cm in size, invading the cecum
© 2007 by the American College of Surgeons Published by Elsevier Inc.
and ascending colon, was excised, and a right hemicolectomy and ileocolostomy were performed. On pathologic examination a well-formed hand (arrow in C) was found, along with a long bone and its marrow (long arrow in D) and a flat bone (short arrow in D), representing malformed humerous and scapula, respectively. Histologically, gastrointestinal mucosa was also found. The patient did well postoperatively, and was discharged home. Fetus-in-fetu is a rare malformation, with fewer than 100 cases reported in the English literature.1 It is a
378
ISSN 1072-7515/07/$32.00 doi:10.1016/j.jamcollsurg.2006.08.027
Vol. 205, No. 2, August 2007
monozygotic, monochorionic, diamniotic parasitic fetus that implants within its twin sibling. Prognosis is excellent, as malignant degeneration is rare.2 During fetal development, vitelline circulation anastomoses cause a ‘twin-to-twin transfusion’ syndrome from the nondominant to the dominant twin, resulting in impaired growth of the fetus, which progressively embeds itself within its twin sibling during the third week of gestation. The evolution of the twin fetus usually arrests at the first trimester, although some structures such as intrathoracic organs (lung, heart, thymus), intraabdominal organs (liver, spleen, kidneys, adrenals, and pancreas), and gonads have been described.3 Ectoderm-derived tissues are better represented than endo- or mesoderm-derived tissues; 91% contain vertebral column elements, 82% limbs, 56% central nervous system, and 45% gastrointestinal elements.3 Studies of gonads, red cell antigens, and chromosomes have invariably shown monozygosity between host and fetus.1 The host rarely presents with any associated anomalies, except those related to mass effect of a space-occupying lesion. First noted in the early 1800s by Young,4 fetus-in-fetu was originally described as an intraabdominal mass with rudimentary spinal architecture. Teratoma is a disorga-
Kaufman et al
Images for Surgeons
379
nized array of pluripotent cells, representing all three germ layers, that, unlike fetus-in-fetu, does not develop past the primitive streak stage (days 12 to 15). It was only in the 1930s that teratoma was recognized as a separate entity.5 Since then, the definition of fetus-in-fetu has evolved to include metameric segmentation, and craniocaudal, body coelom, and systemic organo-genesis.5,6 Differentiation of these two entities is of paramount importance, because teratoma has substantial malignant potential while fetus-in-fetu is rarely malignant.
REFERENCES 1. Brand A, Alves MC, Saraiva C, et al. Fetus-in-fetu–diagnostic criteria and differential diagnosis–a case report and literature review. J Pediatr Surg 2004;39:616–618. 2. Hopkins KL, Dickson PK, Ball TI. Fetus-in-fetu with malignant recurrence. J Pediatr Surg 1997;32:1476–1479. 3. Hoeffel CC, Nguyen KQ, Phan HT, et al. Fetus-in-fetu: a case report and literature review. Pediatrics 2000;105:1335–1344. 4. Young GW. Case of a fétus found in the abdomen of a boy. Med Chir Trans 1809;1:234. 5. Willis RA. The structure of teratoma. J Pathol Bacteriol 1935;40: 1–36. 6. Eng HL, Chuang JH, Lee TY, Chen WJ. Fetus-in-fetu: a case report and review of literature. J Pediatr Surg 1989;24:296–299.
A
B
C
D
A 2-year-old boy presented with a 5-month history of postprandial abdominal pain and bloody stools. He had previously undergone laparoscopic exploration for an undescended right testicle. Physical examination showed a grapefruit-sized, firm, nontender, solid mass in the right lower quadrant, without erythema or discoloration of the overlying skin. Laboratory tests and chest x-ray were normal. CT scan and MRI of the abdomen showed a large, complex, soft-tissue mass with bony elements (arrows in A and B). At laparotomy a retroperitoneal mass, 12 ⫻ 15 cm in size, invading the cecum
© 2007 by the American College of Surgeons Published by Elsevier Inc.
and ascending colon, was excised, and a right hemicolectomy and ileocolostomy were performed. On pathologic examination a well-formed hand (arrow in C) was found, along with a long bone and its marrow (long arrow in D) and a flat bone (short arrow in D), representing malformed humerous and scapula, respectively. Histologically, gastrointestinal mucosa was also found. The patient did well postoperatively, and was discharged home. Fetus-in-fetu is a rare malformation, with fewer than 100 cases reported in the English literature.1 It is a
378
ISSN 1072-7515/07/$32.00 doi:10.1016/j.jamcollsurg.2006.08.027
Vol. 205, No. 2, August 2007
monozygotic, monochorionic, diamniotic parasitic fetus that implants within its twin sibling. Prognosis is excellent, as malignant degeneration is rare.2 During fetal development, vitelline circulation anastomoses cause a ‘twin-to-twin transfusion’ syndrome from the nondominant to the dominant twin, resulting in impaired growth of the fetus, which progressively embeds itself within its twin sibling during the third week of gestation. The evolution of the twin fetus usually arrests at the first trimester, although some structures such as intrathoracic organs (lung, heart, thymus), intraabdominal organs (liver, spleen, kidneys, adrenals, and pancreas), and gonads have been described.3 Ectoderm-derived tissues are better represented than endo- or mesoderm-derived tissues; 91% contain vertebral column elements, 82% limbs, 56% central nervous system, and 45% gastrointestinal elements.3 Studies of gonads, red cell antigens, and chromosomes have invariably shown monozygosity between host and fetus.1 The host rarely presents with any associated anomalies, except those related to mass effect of a space-occupying lesion. First noted in the early 1800s by Young,4 fetus-in-fetu was originally described as an intraabdominal mass with rudimentary spinal architecture. Teratoma is a disorga-
Kaufman et al
Images for Surgeons
379
nized array of pluripotent cells, representing all three germ layers, that, unlike fetus-in-fetu, does not develop past the primitive streak stage (days 12 to 15). It was only in the 1930s that teratoma was recognized as a separate entity.5 Since then, the definition of fetus-in-fetu has evolved to include metameric segmentation, and craniocaudal, body coelom, and systemic organo-genesis.5,6 Differentiation of these two entities is of paramount importance, because teratoma has substantial malignant potential while fetus-in-fetu is rarely malignant.
REFERENCES 1. Brand A, Alves MC, Saraiva C, et al. Fetus-in-fetu–diagnostic criteria and differential diagnosis–a case report and literature review. J Pediatr Surg 2004;39:616–618. 2. Hopkins KL, Dickson PK, Ball TI. Fetus-in-fetu with malignant recurrence. J Pediatr Surg 1997;32:1476–1479. 3. Hoeffel CC, Nguyen KQ, Phan HT, et al. Fetus-in-fetu: a case report and literature review. Pediatrics 2000;105:1335–1344. 4. Young GW. Case of a fétus found in the abdomen of a boy. Med Chir Trans 1809;1:234. 5. Willis RA. The structure of teratoma. J Pathol Bacteriol 1935;40: 1–36. 6. Eng HL, Chuang JH, Lee TY, Chen WJ. Fetus-in-fetu: a case report and review of literature. J Pediatr Surg 1989;24:296–299.