Oropharyngeal fetus in fetu.

Fetus in fetu is an extremely rare entity and refers to the growth of a "parasitic" twin within a more mature fetus due to its inclusion within cells of the blastocyst. The presence of a vertebral column is considered essential for the diagnosis of a fetus in fetu. The retroperitoneum is the most common location for a fetus in fetu and its location in the mouth is rare. We report a case of oropharyngeal mass detected on antenatal sonography with imaging features consistent with a fetus in fetu. Complete surgical removal of the mass was aided by imaging. Follow-up of these patients is recommended to detect the rare incidence of malignant degeneration.