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

Fetus in fetu is a rare, nonviable, malformed parasitic twin, which grows within the body of its partner. It has been known as being almost always anencephalic and rarely reported to have an immature teratoma component. We report a case of a sacrococcygeal fetus-in-fetu with brain tissue seen on both imaging studies and pathologic specimens, containing an immature teratoma component on pathologic examinations. Imaging studies including plain radiography were very helpful for the correct diagnosis. [ABSTRACT FROM AUTHOR]