Infantile hemangioendothelioma of the liver is seen in fetuses and newborns and consists of a large number of endothelium-covered vascular ducts in the liver. It should not be confused with epithelioid hemangioendothelioma of the liver, which occurs in older patients.
Epidemiology.
Hemangioendothelioma occurs in fetuses and newborns and is detected in utero as early as 16 weeks of gestation. It is the most common hepatic mass in infants (<6 months of age).
Clinical presentation.
Angioendothelioma has a large number of arteriovenous shunts and may lead to fetal cardiovascular damage and fetal edema. It can manifest as hepatomegaly, as in most cases it spreads to the entire liver.
In addition, the fetus may develop hemolytic anemia, thrombocytopenia, and wasting coagulopathy (Kasabach-Merritt sequelae).
If these tumors are not detected prenatally, the newborn may present with unexplained congestive heart failure.
Pathology.
Vascular endothelioma is histologically distinct from hemangioma and hemangiosarcoma. There is elevated serum AFP in 3% of cases.
Associations.
Hypothyroidism: This may be due to the high type 3 iodothyronine deiodinase activity produced by the hemangioma.
In 10% of cases there are imaging features of hemangioma at other sites.
Ultrasound.
Pediatric hemangioendotheliomas have multiple ultrasound presentations and can be hypoechoic or strongly echogenic or have mixed echogenic reflections with prominent vascular ducts.
Color Doppler ultrasonography will show increased blood flow.
CT.
With progressive filling, there is typical marginal enhancement. Another characteristic finding is a decrease in the caliber of the aorta under the abdominal branches (middle aortic syndrome) because of the distribution of vessels mainly towards the liver. The same process would lead to an excessive enlargement of the abdominal trunk and hepatic arteries.
MRI.
Multifocal hemangiomas present as spherical lesions with homogeneous signal intensity on MRI. There is usually a large amount of flow space. Typical signal characteristics include.
T1: low signal; T2: high signal.
Treatment and prognosis.
The natural history of hemangioendothelioma in infancy is a rapid, proliferative growth phase during the first 6 months of life, followed by retraction and regression (usually between the 12th and 18th months of life).
If the child remains asymptomatic, treatment may not be necessary.
If symptoms of high-output heart failure develop, the first line of treatment is corticosteroids, which are thought to cause vasoconstriction of abnormal blood vessels.
Treatment is varied and depends on the site and extent of tumor involvement, the site of metastasis, and specific individual factors. Surgical resection, radiation therapy, and chemotherapy have all been used to treat these masses, although studies of survival have not led to the development of various treatment options.