Large hepatic mesenchymal hamartoma leading to mid-trimester fetal demise.

This report describes a fetus with a large multiloculated cystic liver mass. Two small abdominal cysts were seen on ultrasound at 19 weeks of gestation but the patient was referred to us at 23 weeks, after the mass had grown to 8.0 x 5.6 x 7.0 cm, displacing intra-abdominal organs, heart and diaphragm. There was a small amount of ascites but no hydrops. There was polyhydramnios and a thick hyperechoic placenta. After detailed sonograms and MRI suggested the diagnosis of cystic mesenchymal hamartoma of the liver, cyst decompression was favored and consent was obtained. Unfortunately, absence of fetal cardiac activity was noted on the day of the planned intervention. Autopsy confirmed the diagnosis and demonstrated placental changes consistent with mesenchymal stem villous hyperplasia of the placenta. Large fetal cystic abdominal masses that compress the heart, lungs and other organs may benefit from prenatal decompression. This is the first report of cystic hamartoma of the liver apparent on second-trimester sonography, and the fourth time such a lesion is associated with fetal or neonatal death out of 11 cases diagnosed prenatally.