Fetus-in-fetu: report of a case and a review of the literature.

A 2-week-old girl was found to have an asymptomatic abdominal mass on routine examination. Surgical removal revealed the mass to have 4 limb buds situated relative to a palpable vertebral column. Karyotyping revealed the mass to be 46 XX. The mass was therefore diagnosed as a case of fetus-in-fetu. The literature on this rare entity is reviewed, and the diagnosis and pathogenesis of the disease are discussed.