**1. Introduction**

Liver tumors constitute 1–4% of all solid tumors in children, of which 40% are benign. They mainly include hemangioma, liver hamartoma, and liver cell adenoma. Malignant tumors mainly include hepatoblastoma (HB), hepatocellular carcinoma (HCC), malignant liver

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

mesothelioma, and rhabdomyosarcoma [1]. For most hepatic malignancies, hepatectomy or liver transplantation is optimal for cure. Resectability can be limited by multifocality, bilobar involvement, vascular thrombus or vascular invasion, extension to hepatic hilum, and distant metastasis [2]. If the tumor cannot be resected at initial imaging evaluation, the child is usually first treated with chemotherapy and/or radiation, and then re-imaged. For this reason, proper imaging evaluation of the liver is necessary which will shorten the surgical waiting duration and increase the success of the resection. In the cases where liver resection has high morbidity and high incidence, liver transplantation is recommended.

Imaging plays crucial roles in the management of pediatric patients with suspected liver tumors. MR imaging is recommended for children than computed tomography (CT) because of less radiation [3, 4]. However, CT could clearly show the liver anatomy and be helpful in staging, which is widely used in preoperative evaluation in the pediatric patients [3, 5]. Moreover, if the CT or MR imaging indicates a malignant mass, CT of the chest should be performed to assess the presence of lung metastasis [6].

Metastasis may be seen in lymph nodes and lung parenchyma; it is rare in the brain and bones [11]. Twenty percent of HBs present with metastasis and most of them are in the lungs; there-

**Figure 1.** CT and three-dimensional reconstructed liver of PRETEXT II hepatoblastoma resectable at diagnosis (white

Imaging Evaluation of Liver Tumors in Pediatric Patients http://dx.doi.org/10.5772/intechopen.73855 59

The incidence of HCC in children was 0.5–1.0 cases per million children [12]. Different from HB, the median age of occurrence in children with HCC is 10 to 11.2 years [3]. The male to female ratio is 2:1 in young children, but it increases with age. Unlike adults, in whom HCC usually accompanies underlying liver disease, only 20–35% of children with HCC children have underlying liver disease [13]. HCC in children is now considered a distinct tumor family consisting of adult type HCC and variants, fibrolamellar HCC, and transitional liver cell tumor [14]. HCC is usually multifocal and may present with a variable number and distribu-

In fibrolamellar HCCs, tumor cells are circumscribed by bundles of acellular collagen. This form is seen more frequently in adolescents than in adults and has better prognosis. HCCs are highly variable and show non-characteristic features on CT imaging: the tumors may be homogeneous or heterogeneous, solitary or multifocal, well- or ill-defined. On unenhanced CT images, HCCs typically appear isodense or slightly hypodense relative to liver parenchyma. On enhanced CT, they show early arterial contrast enhancement and rapid washout. HCCs are often inconspicuous on delayed scans. HCC sometimes invades the vasculature in the liver, and even the inferior vena cava may be seen [11]. The diagnosis of underlying cirrhosis may help during differential diagnosis, but it is rare in children. Three-dimensional CT image (**Figure 2**) analysis techniques are now available to estimate tumor volume and provide detailed information regarding the intrahepatic anatomy that resembles the actual intraoperative findings [15]. CT volumetry may permit calculation of resected tumor volume and anticipated size of the remnant liver in planning resection [16]. Plain CT of the chest should be performed to rule out the lung metastases. As for HB, tumor staging is an important consideration in determining the plan of treatment and prognosis. The PRETEXT staging system is recommended because it is currently the only staging system that allows surgical planning [9]. HCC is relatively chemoresistant. Complete resection or liver transplantation of localized tumor is the best option. In the SIOPEL-1 report, the overall resection rate was 36% and the 5 y OS and EFS was 28 and 17% respectively [13]. For liver transplantation, patient survival was

tion of tumor nodules. Recognizing HCC lesions smaller than 1.0 cm is still difficult.

fore CT chest is necessary for staging.

arrow).

**2.2. Hepatocellular carcinoma (HCC)**

In our experience, three-dimensional imaging can significantly improve the resection rate of pediatric tumors and increase the safety of the surgery [7]. In our center, we prefer CT scans for preoperative evaluation of pediatric liver tumors. However, it is very important to avoid non-contrast and multiphase images, and use low-dose CT scan in pediatric patients. CT phase of portal venous are very useful for evaluation of primary malignant liver tumors in children.
