**2. Common malignant liver tumors in pediatric patients**

#### **2.1. Hepatoblastoma (HB)**

HB comprises 1% of all pediatric malignancies. HB most often occurs in infants and young children between 6 months and 4 years old. The median age of occurrence is 18 months. After 5 years of age, it becomes rare but histologically more aggressive in children over 8 years old. It occurs equally in males and females [8]. Based on radiological imaging, preoperative staging system (Pretreatment Extent of Disease or PRETEXT) which define extent of liver parenchyma involvement is an important guideline for treatment selection [9]. The new international surgical guidelines, which are being developed for the upcoming Pediatric Hepatic International Tumor Trial, will recommend primary surgical resection at diagnosis for PRETEXT I and II tumors of which the radiographic margin on the middle hepatic vein is wide [10].

As staging and treatment are mainly dependent on imaging, high-quality radiographic imaging has come to be of vital importance. For imaging assessment, both contrast-enhanced CT and MRI are recommended. Non-contrast CT typically shows a relatively well-defined, heterogeneous mass, slightly hypodense compared with liver tissue, with or without calcifications. On contrast-enhanced CT (**Figure 1**), the tumor reveals a heterogeneous enhancement, which may be hyperdense relative to liver parenchyma in the early arterial postcontrast phase and usually appears iso- or hypodense on delayed images (11). Invasion of the portal vein and its subsequent thrombosis must be evaluated in all suspected cases of hepatoblastoma. The tumor thrombus can even spread along IVC and encroach in the lumen of right atrium.

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

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; therefore CT chest is necessary for staging.

#### **2.2. Hepatocellular carcinoma (HCC)**

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

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

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

HB comprises 1% of all pediatric malignancies. HB most often occurs in infants and young children between 6 months and 4 years old. The median age of occurrence is 18 months. After 5 years of age, it becomes rare but histologically more aggressive in children over 8 years old. It occurs equally in males and females [8]. Based on radiological imaging, preoperative staging system (Pretreatment Extent of Disease or PRETEXT) which define extent of liver parenchyma involvement is an important guideline for treatment selection [9]. The new international surgical guidelines, which are being developed for the upcoming Pediatric Hepatic International Tumor Trial, will recommend primary surgical resection at diagnosis for PRETEXT I and II

As staging and treatment are mainly dependent on imaging, high-quality radiographic imaging has come to be of vital importance. For imaging assessment, both contrast-enhanced CT and MRI are recommended. Non-contrast CT typically shows a relatively well-defined, heterogeneous mass, slightly hypodense compared with liver tissue, with or without calcifications. On contrast-enhanced CT (**Figure 1**), the tumor reveals a heterogeneous enhancement, which may be hyperdense relative to liver parenchyma in the early arterial postcontrast phase and usually appears iso- or hypodense on delayed images (11). Invasion of the portal vein and its subsequent thrombosis must be evaluated in all suspected cases of hepatoblastoma. The tumor thrombus can even spread along IVC and encroach in the lumen of right atrium.

tumors of which the radiographic margin on the middle hepatic vein is wide [10].

and high incidence, liver transplantation is recommended.

performed to assess the presence of lung metastasis [6].

**2. Common malignant liver tumors in pediatric patients**

in children.

**2.1. Hepatoblastoma (HB)**

58 Liver Research and Clinical Management

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

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

**3. Value of CT scan in guiding the surgical treatment**

scanning [11].

software (**Figure 4**).

navigation system.

The objective of surgery is to achieve complete resection of the tumor, both macro- and microscopically, which is paramount for cure of malignant liver cancers. The liver resection strategy is based on pre-operative understanding of liver segmentation, vascular occlusion techniques, and experience in performing different types of hepatectomy, including extensive resection (left and right trisegmentectomies). Although abdominal CT should only be considered if MR imaging is not available or contraindicated, there are some limitations of MRI in some hospitals at developing countries. In our experience, MRI is the best available technique for diagnosing liver tumors, but its value is less clear in preoperatively evaluating the resectability of liver tumors especially in pediatric patients. The development and rapid clinical acceptance of single-detector helical CT during the last decade and, more recently, the introduction of multidetector CT (MDCT) have resulted in significant improvements in the study of the liver. MDCT makes it possible to precisely image the vascular anatomy, including the anomalous branches, feeding arteries, or drainage veins. Moreover, each image phase could be independently and simultaneously extracted or combined. In addition to technical advances, such as shorter scanning times, multiplanar imaging, and improved ability to perform multiphasic contrast-enhanced studies, newer and better intravenous contrast media and advances in post-acquisition data processing techniques have renewed researchers' enthusiasm for using hepatic CT

Imaging Evaluation of Liver Tumors in Pediatric Patients http://dx.doi.org/10.5772/intechopen.73855 61

Furthermore, the software program for volumetry provides a proposed remnant liver volume and an optimal cut line of the liver. Various preoperative simulations can thus be considered. This volumetric analysis positively contributes to the safety of the procedure by assisting in the selection of the optimal operations. Preoperative evaluation of the relationship between the tumor and surrounding vasculature was simulated to perform liver resection with 3D

**Figure 4.** Three-dimensional reconstructed liver indicating total liver volume, liver tumor volume, and intraoperative

**Figure 2.** CT of hepatocellular carcinoma in pediatric patient.

63% at 5 years and 58% at 10 years in a study of orthotopic liver transplantation in 41 HCC children <18 years. Recurrence was the primary cause of death in 86% [17]. The outcomes of liver transplantation in HCC are not as good as that for HB.

#### **2.3. Pediatric hepatic sarcomas**

Pediatric hepatic sarcomas include undifferentiated embryonal sarcoma (UES), biliary rhabdomyosarcoma, and angiosarcoma [5]. UES is a rare malignant neoplasm, and its the incidence is higher than the other two types of sarcoma. UES was recently shown to share genetic features with mesenchymal harmatoma. Diagnosis of UES is usually between 6 and 10 years but some studies report presentation in young teenagers [18]. The tumor appears on ultrasound as a hetero-echoic mass, and a hypodense multicystic lesion on CT scan or MRI (**Figure 3**), usually exceeding 10 cm in size, with a predominance for involving the right hepatic lobe [19].

**Figure 3.** CT and three-dimensional reconstructed liver of undifferentiated embryonal sarcoma.
