In order of frequency, the liver accounts for approximately 6% of all abdominal tumors, and is third after the kidneys and adrenal glands for the occurrence of abdominal neoplasms in pediatric subjects. Hepatic tumors may be either primary or metastatic; the non-hepatic primary neoplasms that metastasize most frequently to the liver are Wilms' tumor, neuroblastoma, lymphoma and leukemia. Of the primary hepatic tumors, roughly two thirds are malignant in nature.

From the point of view of classification, malignant primary hepatic neoplasms can be distinguished on the basis of their cells of origin and the patient's age at onset. Concerning the cells of origin, liver cancers can be divided into epithelial and mesenchymal neoplasms. The liver malignancies of epithelial origin are more common and include hepatoblastoma (HB) and hepatocellular carcinoma (HCC). Those of mesenchymal origin comprise mainly sarcomas, i.e. angiosarcoma, myxoid mes-enchymal sarcoma and rhabdomyosarcoma. These latter neoplasms are usually undifferentiated, although differentiated forms may occasionally develop.

The age of onset is an important classification parameter. Up to the age of five, the principal liver malignancies are HB and metastases of Wilms' tumor or neuroblastoma. In children older than five years of age, the most frequent neoplasms are HCC, undifferentiated embryonal sarcoma, fibro-lamellar carcinoma and metastases (Table 1).

As in adult patients, other clinical parameters, such as signs, symptoms and a-fetoprotein (AFP) levels, are relevant factors to consider when radio-logically assessing liver malignancy in pediatric subjects.

The fundamental role of imaging is to establish the extent of the lesion and its relationship with the liver's lobular and segmental anatomy, as well as with the vascular structures. This is essential in the preoperative work-up not only because surgery is often the treatment of choice, but also because of the need to monitor the neoplasm's response to chemotherapy and radiotherapy. A wide range of diagnostic methods are available to meet these objectives, including ultrasound (US), computed tomography (CT), magnetic resonance imaging (MRI) and angiography.

Though it is rarely used, direct x-ray of the ab

Table 1. Classification of liver neoplasms in relation to age

Under five years of age

Over five years of age


Hepatocellular carcinoma


Undifferentiated embryonal sarcoma

Mesenchymal hamartoma

Fibrolamellar carcinoma

Metastases from Wilms' tumor or neuroblastoma




domen can reveal hepatomegaly, elevation of the diaphragm, dislocation of the intestinal loops and the presence of calcifications, although this latter sign is non-specific.

US can identify the solid or cystic nature of a neoplasm, although the echo structure of solid lesions provides little information concerning its histology; in this context the use of Color Doppler US can help to ascertain the degree and type of vascularization.

CT and MR imaging are fundamental and irreplaceable tools for the diagnostic assessment of liver neoplasms in pediatric subjects because of their high accuracy in determining the full extent and resectability of a lesion. Of these two imaging modalities, MRI is usually the preferred technique because of the better soft tissue contrast and, importantly, because of the absence of ionizing radiation.

Due to the small size and frequent non-compliance of pediatric subjects, the techniques employed for liver imaging in these patients need to be adapted from those routinely employed in the adult population.

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