fetus in fetus in the sacral sac: report of surgical management case

Background fetus-in-fetu (fif) is a rare congenital malformation, which consists of a fetus mixed with a distinct tissue that is from the other fetus of the twin. fif is defined as a mass containing a vertebral axis that is often associated with other organs or limbs around this central axis. case report the patient was a two days old girl infant who was referred to the taleghani pediatric center of gorgan, iran, due to a mass in sacral area measuring 8.5 x 12.5 cm with soft consistency containing a normal skin colored fluid with blood streaks and hemorrhagic and bruise colored patches since birth. the results of the mother's ultrasound in the fourth month of pregnancy had identified the cyst for the fetus. in the primary results of imaging, the first diagnosis was type 2 sacrococcygeal teratoma (sct). however, results of post-birth graph confirmed the presence of fetal bone structure in the infant's sacrum, so fif was diagnosed for the infant. conclusion current imaging modalities enable accurate diagnosis before surgery. complete resection is generally curative and allows confirmation of the diagnosis.