Hepatoblastoma (HB) is the most common hepatic tumor in young children. Early detection is of utmost importance to facilitate complete resection of the neoplasia and thus to improve the patient's prognosis. Even if adjuvant chemotherapy is administered, prognosis significantly worsens if the tumor cannot be removed completely.
While an important part of children diagnosed with HB does not display any symptoms, patients may also be presented with general symptoms such as anorexia, nausea and emesis, weight loss and impaired development due to overall weakness. Osteopenia is common and frequently leads to pathologic fractures. To a certain degree, the presence of these symptoms does correlate with the tumor's stage. Hence, a significant part of the patients does already have metastasis at the time of diagnosis. The observation of an enlarged abdomen possibly sensitive to pain and a growing abdominal mass should serve as a clear indicator for HB and prompt further diagnostic measures. HB are more often detected in the right lobe of the liver and measure 5 to 25 cm in diameter.
Icterus and cirrhosis are not common symptoms for HB. Neither is an acute abdomen that may, however, be provoked by tumor rupture. In cases of tumor rupture and consecutive intra-abdominal hemorrhage, severe anemia can be detected.
Certain congenital diseases are associated with an increased risk for HB and may therefore point the physician to this disease. These disorders include trisomy 13 and 18, the Aicardi syndrome, the Beckwith-Wiedemann syndrome, the Fragile X syndrome, the Goldenhar syndrome, the Noonan syndrome, the Prader-Willi syndrome, the Prune belly syndrome, the Sotos syndrome, familial adenomatous polyposis, hemihypertrophy and neurofibromatosis type 1.
Diagnosis of HB is based on clinical examination, laboratory results and diagnostic imaging. While the clinical examination should point the physician to a possible hepatopathy, thrombocytosis and an elevated serum level of alpha-fetoprotein are findings that support the suspicion of a hepatic neoplasia. Magnetic resonance imaging (MRI) or computed tomography (CT) scans are applied to confirm the presence of a usually solitary mass in the liver of the patient.
In detail, the following diagnostic measures may lead to a correct diagnosis of HB:
If at all possible, the HB should be completely resected. Partial hepatectomy is required to achieve complete resection, but significantly improves the patient's prognosis.
Chemotherapy is routinely used post-op to prevent recurrences, but may also be of use before surgical intervention to reduce the tumor's size, particularly if the HB is not resectable upon diagnosis. A combined approach of transcatheter arterial chemoembolization and systemic treatment is generally used. The majority of HB responds to cisplatin treatments. Of note, the kidney function needs to be checked before first cisplatin administration and should be monitored during chemotherapy. If the HB involves all liver segments and does not regress to a resectable size under chemotherapy, a total hepatectomy with a consecutive liver transplantation should be considered.
Treatment recommendations differ depending on tumor stage and further clinical findings (reviewed in ). Unifocal, well delimited tumors are considered standard-risk HB. They shall be treated with a cisplatin monotherapy that has been described before . In brief, surgical resection follows four cycles of preoperative chemotherapy and the patient receives two more cycles of chemotherapy after surgery. On the other hand, if a HB is only diagnosed when metastases are already present or the levels of alpha-fetoprotein are below 100 ng/mL, the tumor is defined as a very high-risk HB. Lung metastases are considered to be confirmed if any nodule larger than 10 mm or several nodules with at least one larger than 5 mm are visible in radiographic images. If these criteria are not met, a biopsy should be taken to clarify the nature of doubtful findings. In the case of a very high-risk HB, a weekly induction chemotherapy with cisplatin and doxorubicin is indicated . Any HB that is neither considered standard-risk nor very high-risk, falls into the category of high-risk HB. In these patients, tumor resection is complicated and recurrences are possible. Treatment recommendations have been given elsewhere .
Elevated serum levels of alpha-fetoprotein have been named as a clinical sign for HB, but they may also serve to evaluate response to therapy and to detect possible recurrences.
HB shows locally invasive growth and may metastasize to lungs, CNS and other organs. Therefore, the tumor stage at the moment of diagnosis is the most important factor for the patient's prognosis. If the tumor affects several segments of the liver or is ruptured at the time of diagnosis, the prognosis worsens. Results of histological analysis may also affect the outcome with the fetal pattern being associated with a very good prognosis. These cases usually do not require chemotherapy. On the other hand, the macrotrabecular and anaplastic HB entail a poorer prognosis. The probability of metastasis augments in cases of anaplastic HB. Further indicators for an unfavorable outcome are low initial levels of alpha-fetoprotein (<100 ng/ml) and age (older children have a worse prognosis).
Survival rates are high when the tumor is detected in an early stage and a complete resection is possible. Relapses are rare when a complete resection could be achieved. If the HB is not or only partially resectable, the prognosis worsens considerably and the probability of a recurrence increases. Overall survival rates independent from tumor stage at diagnosis and chosen treatment range between 62% and 70% .
Hepatoblastoma develops due to as of yet unknown causes. Because it mainly affects young children, it may be suspected that noxious agents affecting their mother before conception or during gestation could increase the risk for HB. These noxious agents may then disturb cell proliferation and differentiation in liver development, which gives rise to aberrant proliferation of undifferentiated cells and consecutive tumor growth  . This hypothesis may be supported by the fact that HB is sometimes diagnosed in children suffering from hereditary, congenital comorbidities, however, this holds true for only 5% of HB cases. Most cases are sporadic.
HB is a rare disease with an incidence of approximately 0.5 to 1.5 cases per 1,000,000 children . Other sources report an even lower incidence of 1 case in every 5,000,000 children. HB accounts for about 1% of all pediatric tumors and is the most common pediatric hepatic tumor with percentages ranging from 25% to more than 60%.
Children diagnosed with HB have an average age of somewhat more than 1 year. The vast majority of HB affects children younger than 5 years. Only few cases of HB in adolescents have been reported and even less in adults. Of note, HB cells are occasionally detected in hepatocellular carcinoma. The prognosis of a patient diagnosed with HB worsens with age.
Boys are affected slightly more often than girls and the male to female ratio is about 1.5-2:1 in Europe. Racial differences do exist as the male to female ratio is augmented in Asia (2.9:1) and white children present HB about five times more often than black children. The outcome, however, is usually worse in black children.
If a young child is diagnosed with an intrahepatic mass and does present thrombocytosis and an elevated serum concentration of alpha-fetoprotein, this may be considered pathognomonic for HB . The tumor is generally unifocal and well delimited and does affect the right lobe of the liver more often than the left lobe. Tumor cells may, however, spread through blood vessels beyond the well delimited, pseudoencapsulated tumor. Metastases manifest themselves in the porta hepatis or in the lungs, and while the CNS may be affected, bones rarely are.
A comprehensive classification system for HB has been established based on cellular subtypes, arrangement of cells and molecular markers.
No direct cause of HB could be detected so far. Presumably, noxious agents do affect the mother before conception or during gestation and leave the child predisposed to HB. Various risk factors have been discussed as possible triggers (e.g., drugs of different types, alcohol, tobacco, environmental toxins, but also the mother's reproductive history and birth characteristics) but convincing evidence is still missing .
Although no direct prevention is possible, efforts need to be made in order to detect possible neoplasias in early tumor stages. A close monitoring of children at risk is the best way to achieve this.
If a family history of any predisposing disease (see chapter Presentation) is suspected or can be confirmed, diagnostic measures should be undertaken regularly up to the age of 4 to detect any possibly developing HB early. These measures involve examination of serum concentrations of alpha-fetoprotein and abdominal ultrasonography every 3 to 6 months. This recommendation also applies to children suffering from chronic hepatitis B and advanced liver damage or any other pathologic condition leading to cirrhosis. Premature babies weighing less than 1,500 g and born between weeks 23 and 25 of gestation comprise another risk group that should be regularly examined .
Similar monitoring actions are indicated in patients who survived a HB.
Hepatoblastoma (HB) is the most common pediatric hepatic tumor. It generally affects young children, considerably younger than 5 years, but may also be detected in older children. Although there are several congenital disorders associated with an increased risk for HB, no cause at all can be identified in the majority of HB cases. Overall deterioration of health and unspecific symptoms such as anorexia, nausea and emesis are generally the reason for medical consultation. Since these symptoms usually manifest themselves when the cancer has reached an advanced stage, therapy is rather difficult. The treatment of choice is a complete resection of the tumor, a task that may be facilitated by preoperative chemotherapy. Postoperative chemotherapy is used to avoid recurrences. Only if a complete resection of the HB can be achieved, the prognosis is good.
Although HB is the most common hepatic cancer in children, it is still a rare disease. As is the case with many other types of cancer, no direct cause has been identified.
HB generally affects young children, but may occasionally be detected in adolescents. The overall state of health worsens as the disease progresses, but initial symptoms are rather unspecific and involve loss of appetite, nausea and vomiting. Nevertheless, a physician should be consulted to clarify the origin of these symptoms. If the clinical examination reveals a mass in the upper right part of the abdomen, a liver tumor may be suspected. Blood samples are taken to check the child's blood levels of certain tumor markers and diagnostic imaging helps to visualize the liver and its surrounding organs. If the suspicion is corroborated by the physician's findings, a biopsy may be required, i.e. a small amount of tissue needs to be obtained in order to analyze it.
The prognosis strongly depends on the time of diagnosis. If the cancer is diagnosed early, it may be removed completely and the prognosis is very good. However, if metastases are already present upon diagnosis, the prognosis is poor.