The placenta seems to be molar type and the initial diagnosis was that of a molar pregnancy with fetus.

At the 2nd ultrasound examination at 17 weeks, a genetic amniocentesis was performed that revealed a 46XX normal. Note the change in the appearance of the placenta and the cystic intraabdominal image.

At 20 weeks, the fetus has a normal growth. The molar placenta diagnosis was changed to placental chorioangioma.

At 26 weeks the fetus is at the 10th percentile for growth and a large part of the placenta appears to be a chorioangioma while the rest appears normal. Note the normal appearance of the abdomen on this view.

By 32 weeks, the fetal growth was less then the 10th centile. The following image was obtained in the abdomen on the left side. This round mobile cystic image in the anterior left abdomen and in close relation to the liver. The walls of the mass are echogenic. The bladder is normal.

Also note the evolution of the placenta. 

Other images demonstrated a high velocity flow in the middle cerebral artery, suggestive of fetal anemia. Normal uterine artery flow:

The last examination demonstrated IUGR, oligoamnios, and pathologic Doppler findings including absent diastolic flow in umbilical artery and brain sparing. Interruption of pregnancy was suggested. A newborn below the 10th percentile was delivered. Neonatal evaluation revealed symptoms of abdominal obstruction, the newborn when to surgery. Intestines were normal. The cystic lesion was recognized at pathology to be a hepatic lymphangioma.

Pathology demonstrated a chorioangioma of the placenta.

Sonographic findings: Thick wall cyst or hypoechogenic mass located in or with close relation to the fetal liver. Absent blood flow with Doppler ultrasound⁵.

Associated anomalies: Skin edema, ascites, hydrops and polyhydramnios (anomalies that can be seen with abdominal lymphangiomas)⁶. In this case there was also a placental chorioangioma.

Differential diagnosis: Hepatoblastoma, hamartoma, hemangioma, hepatic adenoma, dermoid cyst, meconium cyst, choledochal cysts, enteric duplication, ovarian cyst, and urinary system obstruction⁷.

Prognosis: benign, if the karyotype is normal and hydrops is absent the prognosis is very good.

Treatment: Although there are some reports of cystic lymphangiomas in other location of the body treated with intrauterine aspirations, local sclerotherapy or injection of fibrin glue, the definitive treatment consist in complete postnatal surgical resection of the lesion, depending on the size of the tumor and its clinical consequences.

References:

1-Deshpande P, Twining P, O'Neil D. Prenatal diagnosis of fetal abdominal lymphangioma by ultrasonography. Ultrasound Obstet Gynecol 2001;17:445-448.

2-Clerici D, Griffa B, Ceppi M, Basilico V, Milvio E. Cystic lymphangioma of the liver. Presentation of a clinical case. Minerva Chir 1989 Apr 15;44(7):1139-41

3-Koh CC, Sheu JC. Hepatic lymphangioma--a case report. Pediatr Surg Int 2000;16(7):515-6.

4-Stavropoulos M, Vagianos C, Scopa CD, Dragotis C, Androulakis J. Solitary hepatic lymphangioma. A rare benign tumour: a case report. HPB Surg 1994;8(1):33-6

5-Garel L, Pariente D, Sauvegrain J. Ultrasound in infancy and childhood. Clin Gastroenterol 1984 Jan;13(1):161-82

6-Van Steenbergen W, Joosten E, Marchal G, Baert A, Vanstapel MJ, Desmet V, Wijnants P, De Groote J. Hepatic lymphangiomatosis. Report of a case and review of the literature. Gastroenterology 1985 Jun;88(6):1968-72.

7-Garel L, Montagne JP, Faure C. Rare pediatric conditions: contribution of grey-scale ultrasonography. Pediatr Radiol 1979 Oct;8(4):237-45