Discussion
While hepatoblastoma is rare, occurring in 1.6 cases per million [1], it is the most common liver tumor in children under 2 years of age [2]. The etiology is unknown, though aberrations in the Wnt signaling pathway have been implicated [3]. The tumor is assumed to originate in utero as the incidence is highest at birth and histologically, hepatoblastoma cells resemble embryonal liver cells [4]. Congenital anomalies can be present in 5.5% of patients [2] and hepatoblastoma has been associated with very low birth weight (<1500g), Beckwith–Wiedemann syndrome, and familial adenomatous polyposis [3]. Obstetrical complications may include premature birth, polyhydramnios, and hydrops [5].
Several cases of hepatoblastoma have been prenatally diagnosed in the literature [5,6,7]. Prenatal diagnosis not only allows for adequate patient counselling, but also coordination with pediatric surgeons, neonatologists, and oncologists at a tertiary care center. The diagnosis is typically made in the third trimester with the visualization of a well-demarcated, solid spherical mass, usually in the right lobe of the liver. This is hypothesized to be related to the lower oxygen tension on the right side supplied by the portal vein, compared to the left side, which is supplied by oxygenated blood from the umbilical vein [6]. The mass may have a “spoke-wheel” appearance on ultrasound. With color Doppler, hepatoblastoma often has a vascular rim, as well as vascularity within the tumor itself. Tumor peak systolic flow of 40 cm/s or more has been associated with a malignant hepatic tumor compared to hemangioma [8].
The differential diagnosis includes hepatocellular carcinoma, mesenchymal hamartoma, hemangioendothelioma, metastatic lesions such as neuroblastoma, leukemia and lymphomatous infiltration [6,7]. Mesenchymal hamartoma, hemangioendothelioma, and vascular tumors are often cystic. On doppler, hepatocellular carcinoma often shows tortuous vessels in the stroma arising from the adjacent parenchyma, but the vascular rim at the periphery is not typical. Metastatic lesions on doppler show a vascular rim, however the stroma is relatively avascular [6].
Previously, reported prenatal cases have had poor outcomes [6,7, 9]. We report a prenatally diagnosed case of hepatoblastoma that went on to receive liver transplant and is alive at 2 years of age. Overall, 5-year survival in patients with hepatoblastoma is 82% [1]. Patients with fetal-predominant histology have better survival outcomes [2]. Approximately two-thirds of patients present with unresectable disease however, hepatoblastoma is chemo-sensitive and these patients receive neo-adjuvant chemotherapy. This renders patients surgically resectable in 75-85% of cases [2,4]. Survival is 70% in patients who receive neoadjuvant chemotherapy, surgical resection and subsequent adjuvant chemotherapy [10]. If they have major vascular involvement or multifocal disease, they may be liver transplantation candidates. Survival in patients who receive liver transplant is anywhere between 65-80% [2,10].
References
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