Halim Berdi Taneh - Faculty Member of Pediatrics Surgery Department , Educational Center of Taleghani, Golestan University of Medical Sciences, Gorgan, Iran.
Maryam Chehrehgosha - Faculty Member of Surgical Technology Department, Paramedical School, Golestan University of medical Sciences, Gorgan, Iran.
Ghorban Mohammad Kochaki - Faculty Member of Surgical Technology Department, Paramedical School, Golestan University of medical Sciences, Gorgan, Iran.
Soheila Kalantari - Faculty Member of Surgical Technology Department, Paramedical School, Golestan University of medical Sciences, Gorgan, Iran.

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 twin. FIF is defined as a mass containing a vertebral axis often associated with other organs or limbs around this central axis.Case report: The patient was a two day old girl infant who due to a mass in a sacrum area measuring 8.5 x 12.5 cm with soft consistency containing a normal skin color fluid with blood streaks and hemorrhagic and bruise colored patches since birt, was admitted at the Taleghani children s Pediatric Center of Gorgan. 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 the diagnosis was type 2 sacrocoxigeal teratoma. However, results of post-birth graphy confirmed the presence of fetal bone structure in the infants s sacrum, so FIF was diagnosed for the infant.Conclusion: In the present study, FIF has been seen in sacrum, which is a very rare case in FIF.

case report, Fetus-in-fetu, Sacrum, Infant