Hepatoblastoma

Hepatoblastoma is the most common primary malignant liver tumour in children under 4 years of age. It is tumour of embryonic origin.

Epidemiology

Most cases are seen during the first 18 months of life and diagnosis in adulthood is exceedingly rare. Occasionally the tumour may be diagnosed antenatally ². There is a recognised slight male preponderance with a M:F ratio of up to ≈ 3:2. There may also be predilection towards the right lobe of the liver.

Clinical presentation

Most children present with abdominal distension or an asymptomatic  palpable abdominal mass. However, other presenting symptoms include ¹:

• abdominal pain
• anorexia
• vomiting
• jaundice 
• pyrexia
• anaemia 
• back pain
• pseudo precocious puberty (due to chronic GnRH secretion) 

Pathology

Macroscopically hepatoblastomas are usually relatively well circumscribed masses, usually single, with heterogeneous cut surface ¹⁰.

Histological classification of hepatoblastoma is complicated with multiple subtypes identified. The notable subtypes include:

• epithelial - most common
• small cell undifferentiated - worst prognosis
• mixed type - calcifications more common in mixed type

It is important to note however, that with the possible exception of small cell undifferentiated subtype, prognosis is independent of histology when adjusted for stage gender and age ¹⁰. 

For full classification please refer to hepatoblastoma histological classification

Associations

It has been known to be associated with :

• Beckwith-Weidemann syndrome ¹
• hemihypertrophy : seen in 2% of patients with hepatoblastoma ¹
• familial adenomatosis polyposis ^3,5
• fetal alcohol syndrome ⁶
• prematurity and low fetal birth weight ^1,6
• Gardner syndrome ⁵
• glycogen storage disease 
• biliary atresia^1-2

Markers

Serum alpha feto protein (AFP) levels are frequently elevated ( 90% of cases ⁶) *. 

Staging

See - hepatoblastoma staging

Caval involvement often indicates unresectable disease

Radiographic features

Plain film

Abdominal x rays are non-specific, typically demonstrating a right upper quadrant  mass. Calcifications are visible in 10% of cases ^1,4.

Ultrasound

On ultrasound, hepatoblastomas appear as predominantly echogenic soft tissue mass. In larger tumours heterogeneity and variable echogenecity is common. Even when large, they tend to be relatively well defined ⁷. Intra-lesional calcifications may be visible as areas of shadowing ^4,7.

CT

Usually seen as a well defined heterogeneous mass, which is usually hypoattenuating compared to surrounding liver ¹¹.  Frequently there are with areas of necrosis and haemorrhage. Chunky, dense calcifications may be seen in approximately 40% of cases ¹¹.

CT is also able to evaluate the lungs for metastases and for nodal enlargement.

MRI

MRI is superior to CT in defining tumour margins, vessel involvement and adenopathy ¹.

• T1 - generally hypo intense
• C+ (Gd) - can show heterogeneous enhancement
• T2 - 
  • generally hyper intense compared to liver
  • areas of necrosis and haemorrhage are common

Angiography

• tend to be hypervascular

Treatment and prognosis

Surgical resection is the treatment of choice although preoperative chemotherapy may be used to reduce tumour bulk. Chemotherapy is also employed in following surgical resections. If the tumour is reselectable then liver transplantation provides a cure, as long as no metastatic disease is present. The lungs are a relatively frequent site of metastases.

Overall there is approximately 65 - 70% long term survival ¹⁰, however prognosis depends on staging:

• stage I - can expect very good long term survival, of up to 100% with combined chemotherapy and surgery ^8,12
• stage II - 75-80%
• stage III - 65%
• stage IV - 0-27% ¹⁰

Differential diagnosis

General imaging differential considerations include

• mesenchymal hamartoma
• infantile haemangioendothelioma
• hepatic metastases : e.g. neuroblatoma
• hepatocellular carcinoma (HCC)
• rhambdomyosarcoma of biliary tract  (rare)