Mesenchymal hamartoma of the liver: a case report.

A 6-month-old boy presented with a large abdominal mass that proved to be a cystic hepatic mesenchymal hamartoma occupying both hepatic lobes. During fetal life, a bulky, abnormal, cystic placenta had been present, which on histological examination was diagnosed as mesenchymal stem villous hyperplasia. This association has not previously been reported.