Clinical History
An 8-month-old girl presented with abdominal enlargement. Clinical examination revealed a palpable mass in the right abdomen. Laboratory examinations showed an abnormally elevated α-fetoprotein (AFP).
Imaging Findings
The patient underwent abdominal US (not presented) and MRI to evaluate the mass. There was a lobular tumour measuring 11 x 12 x 13 cm, which was situated in the right liver lobe.(Fig. 1) The tumour showed inhomogeneous enhancement after IV administration of gadolinium. On delayed T1-weighted images, there were some contrast-enhancing septa. There was also a lung nodule. (Fig. 1) As biopsy proved the mass to be a hepatoblastoma, the patient underwent the SIOPEL-4 protocol. After the completion of chemotherapy, ultrasound showed that the mass had a mixed echogenicity with multiple anechoic areas, which were considered to represent areas of cystic necrosis due to chemotherapy. (Fig. 2) On MRI, the tumour was reduced to 6x8x8 cm. T1-weighted images demonstrated the presence of high signal intensity inside the tumour, which was considered to represent haemorrhagic areas caused by chemotherapy. (Fig. 3) T2-weighted images revealed areas with high signal intensity, consistent with cystic necrosis, as identified with ultrasound.
Discussion
Hepatoblastoma represents the commonest primary malignant liver tumour in children younger than 5 years, with an incidence of 0.6/100000. Less than 5% of hepatoblastomas are congenital. Hepatoblastoma is associated with syndromes like Beckwith-Wiedmann and Gardner. [1, 2] 80% of hepatoblastomas are solitary while 20% are multifocal. [3]
Hepatoblastoma causes abdominal enlargement, anorexia and weight loss. Metastases may affect the lungs, bones, brain, eyes, ovaries and upper abdominal lymph nodes. The tumour may also invade the inferior vena cava. Most patients with hepatoblastoma have elevated α-fetoprotein (AFP), which can be used to monitor treatment or detect recurrence. Regarding differential diagnosis, an elevated AFP excludes the benign nature of a lesion but is not caused by all primary malignancies. [1, 3]
There are two histologic types: the epithelial and the mixed epithelial-mesenchymal type with six different patterns like the fetal or the small cell undifferentiated. [1]
Imaging hepatoblastoma reflects histology and includes a well-circumscribed mass, which may be divided into lobules by septa. Epithelial hepatoblastomas usually appear homogeneous, whereas mixed tumours are heterogeneous due to the presence of osteoid, fibrous and cartilaginous tissue. Abdominal radiographs reveal hepatomegaly or a mass which in cases of mixed tumours may show coarse calcifications due to osteoid tissue.[1] Epithelial hepatoblastomas appear usually homogeneously hyperechoic in ultrasound while mixed type may also contain calcifications or bone causing acoustic shadowing and anechoic areas, which correspond to haemorrhage or necrosis. The tumour’s echogenicity may be similar to a spoke-wheel and contain hypoechoic septa.[1, 3] Doppler technique demonstrates blood vessels with high velocity flow within the mass.[4] On CT, hepatoblastoma is hypodense in both enhanced and unenhanced images, with speckled or amorphous calcifications in most cases. The tumour appears lobulated with septa which may be enhanced along with the periphery of the mass in the arterial phase.[1] As hepatoblastoma is mildly hypervascular, dual or triple-phase CT will not add much to diagnosis and can be avoided for radiation protection purposes.[5] MRI shows epithelial hepatoblastomas with homogeneously slightly low signal intensity on T1-weighted images and high on T2-weighted images. Mixed tumours appear heterogeneous. The fibrotic septa show low signal intensity on T1 and T2 sequences and demonstrate gadolinium enhancement. Haemorrhage shows high signal intensity on T1-weighted images. MRI confidently detects vascular invasion. [1, 2] Percutaneous biopsy can be performed using ultrasound or CT guidance. [5]
Hepatoblastoma is treated with surgery and preoperative chemotherapy when the tumour is unresectable at diagnosis (40%-60% of cases). 85% of these tumours will become resectable after chemotherapy. [6]
Differential Diagnosis List
Biopsy-proven hepatoblastoma (fetal pattern)
Hepatoblastoma
Neuroblastoma metastases
Hepatocellular carcinoma
Infantile haemangioendothelioma / Haemangioma
Hamartoma
Final Diagnosis
Biopsy-proven hepatoblastoma (fetal pattern)
