Hepatic mesenchymal hamartoma associated with mesenchymal stem villous hyperplasia of the placenta.

A rare case of prenatally diagnosed hepatic mesenchymal hamartoma associated with mesenchymal stem villous hyperplasia of the placenta is presented and the literature reviewed. The placenta was noticed to have multiple cysts at 16 weeks' gestation and elevated maternal serum alpha-fetoprotein was present. Cystic liver masses were first detected in the fetus at 34 weeks' gestation. The liver mass showed a progressive enlargement during the third trimester and after birth, necessitating extended left hepatic trisegmentectomy at 3 months of age. Histological examination established the diagnosis of mesenchymal hamartoma of the liver and mesenchymal stem villous hyperplasia of the placenta. This is the first report of this association in which both lesions were diagnosed in utero and confirmed by histology after delivery. The likely pathogenesis of these strikingly similar lesions is discussed. Copyright 2000 S. Karger AG, Basel.