Hepatoblastoma (HB) is a malignant hepatic tumor and is the most common pediatric liver cancer. It is characterized by anorexia, weight loss and an enlarged abdomen. HB is more common in patients with familial adenomatous polyposis (FAP), and can occur in patients with other pre-existing liver conditions. About 5% of HB cases are associated with genetic factors, especially overgrowth syndromes, such as Beckwith-Wiedemann syndrome (BWS) or hemihypertrophy (see these terms).
HB accounts for about 1% of all pediatric tumors and for 2/3 of primary hepatic tumors in children. Its incidence is estimated to be 1/5,000,000 in Europe. A slight male predilection (1.5:1 to 2:1) has been observed.
The age of disease onset lies in infancy or early childhood (median age of occurrence is 1 year and 90% of HB presents before 5 years). Common presenting signs include anorexia and weight loss and, most commonly, an enlarged abdomen. Abdominal pain, nausea and vomiting, and especially jaundice are less frequently observed. FAP and BWS are associated with an increased risk of HB. Trisomy 13 and 18, Goldenhar syndrome, Noonan syndrome, Fragile X syndrome, Sotos syndrome, Prader-Willi syndrome, Prune belly syndrome, Aicardi syndrome and neurofibromatosis Type 1 may also predispose to HB (see these terms). High-risk patients are those with distant metastases, very low initial alpha-fetoprotein (AFP) level (<100 ng/ml), older age (> 8 yrs), tumor rupture at diagnosis and/or tumor involvement of all 4 hepatic sectors.
The etiology of HB is still unknown. However, it is hypothesized to derive from undifferentiated hepatic progenitor cells that undergo malignant transformation during embryogenesis. Mutations of the genes APC (5q21-q22), AXIN1 (16p13.3) and AXIN2 (17q24.1), that prevent degradation of beta-catenin, have been found in syndromic forms of HB but have rarely been described in sporadic HB. However, a high rate of oncogenic mutations of the beta-catenin gene (CTNNB1; 3p21) (50%-90%) has been reported in HB and it is thought to be associated with constitutive activation of the Wnt/beta-catenin signaling pathway.
Diagnosis is based on laboratory findings showing elevated serum AFP level and on magnetic resonance imaging (MRI)/computed tomography (CT) findings showing in 80% of cases solitary masses mostly involving the right lobe (58%). HB ranges in size from a few cm to > 15 cm and generally shows lobulated borders. It can also be multifocal. Pure fetal histology is associated with very good prognosis and may not require chemotherapy, while a small-cell HB variant may be of high risk of metastasis. HB is usually T1 hypointense and T2 hyperintense; fibrous septa appear hypointense on both T1WI and T2WI and show progressive enhancement. Histologically, HB presents epithelial (fetal, embryonal and fetal, macrotrabecular and anaplastic small-cell) or mixed epithelial-mesenchymal in type which frequently co-exist in the same tumor.
Differential diagnosis includes focal nodular hyperplasia, infantile hemangioendothelioma (IHE), pediatric hepatocellularcarcionoma, hemangioma, hepatic cystic hamartoma, undifferentiated embryonal sarcoma of the liver, rhabdomyosarcoma (biliary), and rhabdoid tumor (hepatic) (see these terms).
In most cases complete resection of the tumor can be achieved with a partial hepatectomy. For unresectable tumors, preoperative chemotherapy (systemic or transcatheter arterial chemoembolization (TACE) combined with systemic chemotherapy) is used. Total hepatectomy with liver transplantation is a treatment option for HB in conditions where the tumors remain unresectable after chemotherapy or for multifocal HB invading all 4 sectors of the liver. In most cases postoperative chemotherapy is used routinely.
Prognosis for patients with resectable tumors and no high risk features is fairly favorable (80-90%), whereas the outcome for those with non-resectable or recurrent disease is relatively poor (around 20-30%). Relapse in HB occurs in less than 12% of the children who have achieved complete remission.
Last update: July 2015
- Pr Piotr CZAUDERNA
- Pr Giorgio PERILONGO