[Twin gestation with complete hydatidiform mole and a coexisting live fetus: A case report and review of the literature].

Twin pregnancies with complete hydatidiform mole and coexisting live fetus are very rare, with only about 300 reported cases. This type of pregnancy is considered a high obstetric risk due to the possibility of severe maternal-fetal complications. Although the clinical and ultrasound findings can be highly suggestive of this type of pregnancy, the definitive diagnosis is usually reached by histopathological examination. The differential diagnosis usually includes partial hydatidiform mole and hydropic pregnancies, which can present similar findings in specimens from the first trimester of pregnancy and thus it is important to interpret correctly the differentiating features. The use of immunohistochemistry for p57 can prove very useful, although some cases show an aberrant expression. We present a case of a twin pregnancy with complete hydatidiform mole associated with a live fetus, with magnetic resonance imaging and ultrasound for radiopathological correlation. We discuss the differential diagnosis and the utility of p57 immunohistochemistry.