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Findings: Ultrasound reveals a large, globular, well circumscribed hypoechoic mass within the left lobe of the liver. The blood vessels supplying the mass are tortuous and dilated, and demonstrate nonphasic low resistance brisk blood flow. Parasagittal view of abdominal aorta demonstrates enlarged aortic caliber proximal to the celiac axis, with marked tapering of the aorta distal to the celiac axis.

Coronal T1 weighted views ofthe abdomen demonstrate a large, slightly nodular, well circumscribed mass within the left lobe of the liver. The mass demonstrates slightly heterogenous, but primarily decreased signal intensity with several punctate regions of increased signal intensity, suggestive of focal areas of hemorrhage. The T2 weighted axial views through the liver demonstrate well circumscribed mass within the left lobe of the liver with slightly heterogenous, but primarily increased signal intensity. There are numerous, prominent flow voids within the mass.

Plain films of the abdomen demonstrate hepatomegaly or abdominal mass. Finely speckled calcifications occur in about 50% of cases. CT of the abdomen is more sensitive for detecting calcifications. Findings of CHF may be present on chest radiography. On Doppler ultrasound, hepatic artery and proximal aorta may be enlarged with marked tapering of aorta distal to the celiac artery. Hepatic veins may also be enlarged due to marked blood flow through the lesion.

Non-enhanced CT demonstrates low attenuation mass. Calcifications are present in approximately 15% of the lesions, usually associated with unifocal disease. Following intravenous contrast administration, there is peripheral enhancement of the lesion. Delayed scans may show filling in of central low attenuation area, although usually this center remains hypoattenuating on delayed scans. Large lesions contain areas of infarction or hemorrhage that do not enhance at any time. Multifocal or small lesions without hemorrhage or necrosis frequently enhance completely.

Appearance at MR depends on the presence of hemorrhage or infarction. The lesions are usually heterogenous and of low signal intensity on T1 weighted sequences and demonstrate high signal intensity on T2 weighted sequences. Areas of hemorrhage usually represent extracellular methemoglobin, appearing as high signal intensity on both T1 and T2 weighted pulse sequences.

Differential Diagnosis:Three other liver tumors should be considered: hepatoblastoma, mesenchymal hamartoma, and metastatic neuroblastoma.

Hepatoblastoma is rarely seen in patients less than one year of age. The alpha-fetoprotein level is usually markedly elevated, whereas in cases of infantile hemangioendothelioma, it is usually normal or only mildly to moderately increased. By CT, hepatoblastoma is more heterogenous than infantile hemangioendothelioma, especially after contrast administration.

Mesenchymal hamartomas usually occur in the infant and are not associated with elevated alpha- fetoprotein levels. Mesenchymal hamartomas typically appear as multilocular cystic masses, rarely as a solid lesion. When solid, mesenchymal hamartomas appear as avascular or hypovascular masses on angiography, scintigraphy, and Doppler ultrasound.

Metastatic neuroblastoma may be confused with the multicentric form of infantile hemangioendothelioma. With metastatic neuroblastoma, urinary levels of catecholamines are almost always elevated, while the primary tumor, often an adrenal mass, can be seen. On contrast enhanced CT scans, marked enhancement is usually noted in cases of infantile hemangioendothelioma, while with metastatic neuroblastoma enhancing areas present normal residual liver.

Diagnosis:Infantile Hemangioendothelioma

Discussion: Most patients present between one and six months of age, although the lesion can be identified with prenatal ultrasound. One-third of cases are discovered in the first month of life, while less than 5% of the cases are detected beyond one year of age.

At presentation, most patients have abdominal mass or hepatomegaly. CHF may be a presenting sign or may occur in the course of treatment if a large amount of arteriovenous shunting is present. Natural history of infantile hemangioendothelioma involves a proliferative phase with rapid growth of tumor during the first six months of life, which is followed by spontaneous regression over the course of several months.

Diagnosis and treatment depend upon the signs and symptoms. In asymptomatic child, no treatment may be necessary, although follow-up imaging is recommended in order to demonstrate tumor regression.

Patient's with CHF are treated with prednisone, digoxin, and furosemide. Prednisone appears to accelerate regression of the lesion. If conservative treatment fails, embolization therapy or surgical resection may be necessary.

Liver transplantation is an option in cases with diffuse tumor involvement or uncontrollable CHF.

References:
1. Keslar PI, Buck JL and Selby DH (1993). Infantile hemangioendothelioma of the liver
revisited. Radiographics 13:657.

2. Kirks DR and Cerou KH (1991). Hemangioendothelioma and hemangioma in Practical
Pediatric Imaging, 2nd. ed. (Kirks DR, Ed.). Little, Brown and Co., Boston, MA, p. 809.

3. Pobiel RD and Bissel GS m (1995). Pictorial essay: Imaging of liver tumors in the infant and
child. Pediatric Radiology 25:495.

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