Fetus-in-fetu: imaging and pathologic findings

Abstract

A 3.5-month-old boy was hospitalized because of an abdominal mass found accidentally. On physical examination, a smooth, firm, nontender mass was present in the right upper quadrant. Abdominal ultrasonography revealed a large, hyperechoic, heterogenous mass with clear boundaries, and scarce blood flow. Abdominal CT scan showed a bulky right retroperitoneal mass. Three-dimensional CT imaging demonstrated spine, iliac bone, and long bones of limbs. The mass was excised successfully. After opening the sac it was noted to contain an incompletely developed fetus with grossly visible limbs, clearly discernible male genitalia, hairs, and a poorly formed head. The fetus was connected to the sac via an 8 cm cord-like structure. Microscopic examination of the mass revealed the presence of skin, cartilage, bone, intestine, and cysts with simple cuboidal epithelium. The use of CT scans enhanced the accuracy of pre-operative diagnosis. Identification of the vertebral column and the long bones of limbs are important indications for the diagnosis. Pathologically, fetus in fetu has many characteristics different from teratoma.

Fetus in fetu: use of intraoperative ultrasound for safe excision of a rare entity

“…MRI can better distinguish soft-tissue planes due to enhancement patterns and osseous structures while reducing exposure to ionising radiation. CT imaging is imperative for surgical planning in order to identify surrounding vasculature 12…”

“…A vertebral column is identified in 76% of cases and limbs are seen in 83% of cases 2 9. The mass rarely contains a structure suggestive of a brain 2 12. It is imperative to differentiate between these two entities because teratoma is associated with a 17% chance of malignancy.…”

Fetus-in-fetu in an 8-month-old girl

“…[14][15] In this report, we summarized the imaging performance and postoperative pathologic histology inspection of retroperitoneal FIF which have been published in English from 2010 to 2015. [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] ( Table 1)…”

A Rare Form of Heteropagus Twinning: Three-Armed Infant with Spinal Dysraphism

“…However, these bones are scattered throughout the tumor and never resemble the real limb. If the fetus is located inside the body of its twin, this process occurs in the other twin's body cavities; this condition is termed fetus in fetu [10–12]. Sometimes, a malformed, abnormal fetus enveloped inside its twin may remain totally silent until later ages, or it can cause an intra-abdominal or sometimes an intrathoracic mass.…”