Sacrococcygeal Fetus-in-Fetu Mimicking a Teratoma: A Rare Case with Brain Tissue and an Immature Teratoma Component

Fetus in fetu is a very rare congenital anomaly, which was first described by Meckel in the nineteenth century (1). It is a nonviable, malformed parasitic twin, which grows within the body of its partner. When it is located in the sacrococcygeal region, fetus in fetu can mimic sacrococcygeal teratoma. Fetus in fetu can be differentiated from mature cystic teratoma by identifying the vertebral column or other well developed organs (1). Here, we report a rare case of a sacrococcygeal fetus-in-fetu with brain tissue, containing an immature teratoma component on pathologic examination.