As the second most common malignant liver tumor in childhood, HCC comprises 35 % of all hepatic malignancies in children [22]. HCC is histologically divided into classical and fibrolamellar types. Fibrolamellar HCC is the most frequent histological variation and is commonly observed in children and adolescents [23]. Conditions associated with a high risk for HCC development are α-1-antitrypsin deficiency, Wilson’s disease, hemochromatosis, hereditary tyrosinemia, Fanconi’s anemia, familial adenomatous polyposis and Gardener’s syndrome [1]. As in HB, α-FP is increased in HCC in the majority of patients [24]. Since the tumor is chemoresistant, surgical resection and liver transplantation (in case of unresectable HCC confined to the liver) are the only therapeutic options [25]. At diagnosis, 50 % of patients present with metastases [26], mostly in the lungs (31 %). Extrahepatic tumor extension and vascular invasion are also frequently seen (39 %) [27]. The US echogenicity of HCC is similar to that of the liver, and the CT characteristics are highly variable, either homogeneous or heterogeneous, solitary or multifocal, and well- or ill defined. While in adults the presence of underlying cirrhosis may help in the differential diagnosis, it is rare in the pediatric population [28]. CT is generally used to evaluate the response to treatment, but it cannot be used to estimate tumor viability (Fig. 10.3).

Several articles on the impact of PET/CT in adult HCC have been published, but there are no reports on the use of this imaging technique in pediatric patients. Lee et al. evaluated 138 adult patients with low-grade or high-grade HCC, either newly diagnosed or reevaluated after treatment (tumor resection, transcatheter arterial chemoembolization, radiofrequency ablation, systemic chemotherapy), who underwent 18F-FDG–PET/CT or conventional imaging modalities [29]. The detection rate for lung metastases by ¹⁸F-FDG–PET/CT was lower than that obtained with CT, and for lesions below 1 cm, it diminished dramatically, probably because of the limited resolution. In the detection of lymph node lesions, by contrast, there were no differences between CT and ¹⁸F-FDG–PET/CT. Moreover, ¹⁸F-FDG–PET/CT was significantly superior to bone scan in patients with bone metastases, depicting all bone lesions [29].

Talbot et al. [30] compared ¹⁸F-FDG with ¹⁸F-fluorocholine in the detection and staging of HCC in patients with chronic liver disease and suspected liver nodules. FDG was shown to be significantly more sensitive, especially in the detection of well-differentiated tumors. Although ¹⁸F-FDG was unable to demonstrate focal nodular hyperplasia, it was more sensitive than ¹⁸F-fluorocholine for other malignancies. Consequently, the authors suggested performing PET/CT with both radiopharmaceuticals as the best option [30]. Another study proposed the use of FDG–PET/CT in the assessment of tumor response and tumor viability after interventional therapy (transcatheter arterial chemoembolization) but further investigations on the benefits of this application are warranted [31].

Undifferentiated sarcoma of the liver is the third most frequently occurring hepatic malignancy of childhood. Unlike HB and HCC, in this rapidly growing tumor [2], α-FP levels are usually normal and thus are of no diagnostic relevance. On US but also on CT and MRI, USLs are generally large and solid in appearance. While FDG–PET has been suggested as a valuable method in the evaluation of USL patients during postoperative chemotherapy, it has yet to be confirmed in the literature (Figs. 10.4 and 10.5) [32]. The treatment of choice is chemotherapy followed by resection. Preferential sites of metastases are the lungs and bones [33].

Derived from neuroendocrine cells, carcinoid tumors spread throughout the body, especially to the liver (Fig. 10.6), and often produce functional peptide hormones. Approximately 56 % arise in the gastrointestinal tract followed by the lungs (30.1 %), pancreas (2.3 %), reproductive system (1.2 %), biliary tract (1.1 %), and head and neck (0.4 %). Primary hepatic carcinoid tumors (PHCT) are extremely rare [34]. Neither CT, nor MRI is advantageous in the imaging of neuroendocrine tumors (NETs), which are generally better detected by OctreoScan scintigraphy [35]. Recent data indicated that higher quality images obtained with a shorter acquisition protocol are possible with ⁶⁸Ga-DOTA-NOC PET/CT than with 111In-DTPA-octreotide [36]. ¹⁸F-FDG–PET may be useful for identifying NETs characterized by rapid growth or aggressive behavior, with increased tumor uptake of the FDG tracer indicative of a worse prognosis. Although NETs with multiple tumor sites show broad-ranging heterogeneity in tracer uptake, FDG–PET may be able to detect unsuspected distant metastases, contributing to better staging of advanced disease [37].