Table 1. Risk Factors Associated With Hepatoblastoma and Hepatocellular Carcinoma continued...
Hepatoblastoma is most often unifocal, and resection is often possible. Hepatocellular carcinoma is often extensively invasive or multicentric, and less than 30% are resectable. Orthotopic liver transplantation has been successful in selected children with hepatocellular carcinoma.
Tumor marker–related factors
Ninety percent of patients with hepatoblastoma and two-thirds of patients with hepatocellular carcinoma have a serum tumor marker, AFP, which parallels disease activity. The level of AFP at diagnosis and rate of decrease in AFP during treatment should be compared with the age-adjusted normal range. Lack of a significant decrease of AFP levels with treatment may predict a poor response to therapy. Absence of elevated AFP levels at diagnosis occurs in a small percentage of children with hepatoblastoma and appears to be associated with very poor prognosis, as well as with the small cell undifferentiated variant of hepatoblastoma. Some of these variants do not express INI1 due to INI1 mutation and may be considered rhabdoid tumors of the liver; all small cell undifferentiated hepatoblastomas should be tested for loss of INI1 expression by immunohistochemistry.[46,49,50,51,52,53]
Beta-hCG levels may also be elevated in children with hepatoblastoma or hepatocellular carcinoma, which may result in isosexual precocity in boys.[54,55] Extremely high levels of beta-hCG are associated with infantile choriocarcinoma of the liver.
Undifferentiated Embryonal Sarcoma of the Liver
Undifferentiated embryonal sarcoma of the liver (UESL) is the third most common liver malignancy in children and adolescents, comprising 9% to 13% of liver tumors. It presents as an abdominal mass, often with pain or malaise, usually between the ages of 5 and 10 years. Widespread infiltration throughout the liver and pulmonary metastasis are common. It may appear solid or cystic on imaging, frequently with central necrosis. Distinctive features are characteristic intracellular hyaline globules and marked anaplasia on a mesenchymal background. Many UESL contain diverse elements of mesenchymal cell maturation, such as smooth muscle and fat. Undifferentiated sarcomas and small cell undifferentiated hepatoblastomas should be examined for loss of INI1 expression by immunohistochemistry to help rule out rhabdoid tumor of the liver.
It is important to make the diagnostic distinction between UESL and biliary tract rhabdomyosarcoma because they share some common clinical and pathologic features but treatment differs between the two, as shown in Table 2. (Refer to the PDQ summary on Childhood Rhabdomyosarcoma Treatment for more information.)