Age-related features and imaging markers
Primary liver tumors are uncommon in pediatric practice, and malignant lesions in the first months of life are extremely rare. For children under 3 years of age, vascular neoplasms, hepatoblastomas, mesenchymal hamartomas, as well as teratomas and rhabdoid tumors, are most characteristic. In patients older than three years, diagnoses typical of adults prevail.
Certain imaging characteristics help narrow down the diagnostic search:
- Fat inclusions: considered an almost pathognomonic sign of teratoma.
- Ossification: visualized in hepatocellular carcinoma (HCC) and teratomas.
- Solid areas with cystic-like zones: the presence of low-density areas on CT or hyperintense signal on T2-weighted MRI requires the exclusion of undifferentiated sarcoma.
- Calcification: is not a reliable differential criterion, as it occurs in a wide range of pathologies (infections, HCC, hepatoblastoma, congenital hemangioma, teratoma).
Hepatoblastoma
This malignant neoplasm is rarely detected immediately after birth or in children over three years of age. The disease can be associated with biliary atresia and Beckwith–Wiedemann syndrome.
Laboratory tests typically reveal thrombocytosis and an age-inappropriate elevation in alpha-fetoprotein (AFP) levels. It is important to remember that AFP also rises in yolk sac tumors.
Imaging and staging features:
- On MRI, the tumor appears as a large heterogeneous mass.
- T2-weighted MRI can reveal diaphragmatic infiltration and secondary pleural effusion.
- A key step in local staging is assessing the tumor's relationship with the hepatic veins (it is optimal to use the MinIP MRI mode).
- Final staging takes into account the number of intact adjacent liver segments, vascular invasion, capsule integrity, and the presence of distant metastases (predominantly to the lungs).
Vascular neoplasms
Infantile hepatic hemangioma demonstrates non-infiltrative growth without perifocal edema and is often combined with multiple cutaneous hemangiomas. Ultrasound with Doppler mapping reveals low vascular resistance and high blood flow velocity (sometimes with arteriovenous shunting), which can hemodynamically lead to high-output heart failure. Gadolinium-enhanced MRI is characterized by centripetal contrast enhancement.
Congenital hemangiomas resemble infantile ones on imaging but may be complicated by thrombosis and the formation of vascular aneurysms. Two types are distinguished:
- Rapidly involuting congenital hemangioma (RICH): completely regresses by approximately 14 months of life. On CT/MRI, it may demonstrate thick, uneven ring-like enhancement.
- Non-involuting congenital hemangioma (NICH): does not undergo spontaneous regression.
Mesenchymal hamartoma and metastases
Mesenchymal hamartoma typically presents as a palpable mass in children under 2 years of age. Most often, it is a mixed cystic-solid mass capable of reaching giant proportions and encasing large vessels (e.g., the inferior vena cava and portal vein). In the youngest patients, the hamartoma may have a completely solid structure. Multifocal forms occur.
Metastatic involvement (secondary masses): In children, the liver is most frequently metastasized by neuroblastoma (can cause massive diffuse infiltration where the liver wraps around the spleen and stomach), nephroblastoma (Wilms tumor), sarcomas, and lymphoproliferative disorders.
When detecting a multifocal lesion, the differential diagnosis includes not only metastases but also infections, regenerative nodules, focal nodular hyperplasia (FNH), peliosis hepatis, angiomyolipomas, and multiple vascular tumors.
Briefly: answers to topical questions
Which genetic syndromes and developmental anomalies are associated with the occurrence of hepatoblastoma?
The occurrence of hepatoblastoma is associated with the following genetic syndromes and developmental anomalies:
- Beckwith–Wiedemann syndrome (Beckwith–Wiedemann syndrome).
- Biliary atresia.
- Hemihypertrophy.
- Familial adenomatous polyposis.
- Meckel's diverticulum.
- Fetal alcohol syndrome.
On which anatomical criteria is the PRETEXT international radiological staging system for hepatoblastoma based?
Radiological staging of hepatoblastoma is based on assessing liver segment involvement and invasion of surrounding anatomical structures. Staging criteria include:
- Number of adjacent liver segments not affected by the tumor.
- Presence of vascular encasement or invasion (assessment of the tumor's relationship with the hepatic veins is the basis for local staging).
- Capsular rupture.
- Presence of metastases (most commonly to the lungs, making chest CT mandatory).
Which hepatospecific contrast agents are used for differential MRI diagnosis of liver masses in children?
For MRI characterization of focal liver lesions, hepatobiliary specific contrast agents are described, which target:
- Hepatocytes: an example is gadoxetic acid (gadoxetic acid), which is taken up by hepatocytes and partially excreted into the biliary tract; it is used, in particular, to differentiate FNH from adenoma.
- Reticuloendothelial system (RES): iron oxide-based agents, including ultrasmall superparamagnetic iron oxide particles (USPIO), primarily target RES cells and cause T2 relaxation time shortening.
Class and exam questions
Which liver masses should be suspected in a child under 3 years of age in the first place?
At this age, infantile hemangiomas, mesenchymal hamartomas, hepatoblastomas, as well as teratomas and rhabdoid tumors are most common.
Can the presence of calcifications provide a definitive diagnosis?
No, calcification in pediatric liver masses is not a reliable differential sign. It can be detected in hepatoblastoma, carcinoma, teratoma, infectious processes, and hemangiomas.
What is the difference between infantile hemangioma and congenital hemangioma on imaging?
They are very similar, but congenital hemangiomas are more frequently characterized by the presence of vascular aneurysms and thrombosis. In addition, the rapidly involuting form (RICH) may show specific thick ring-like contrast enhancement.
Why is a chest CT scan mandatory in hepatoblastoma?
Hepatoblastoma most frequently metastasizes to the lungs. Chest CT is a mandatory standard for correct disease staging.
What else to study on this topic
- Imaging diagnostics of biliary atresia and hepatic hilum cysts
- Complications after liver transplantation: PTLD and vascular stenoses
- Traumatic liver injuries and battered child syndrome in pediatrics
- Differential diagnosis of causes of surgical jaundice in infants
- Normal ultrasound anatomy and dimensions of the biliary tract in pediatrics
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