Hepatic hemangiomas are benign, hypervascular, venous malformations that occur in the liver. They are the most common benign mesenchymal tumors of the liver. Hemangiomas are lined by endothelial cells with a thin fibrous stroma. They are also known as cavernous or capillary hepatic hemangiomas. They are generally asymptomatic and incidentally found on imaging. Often found as solitary lesions, but multiple lesions may also be present. They are categorized by size. Small hemangiomas are 1 cm to 2 cm, typical hemangiomas are 2 cm to 10 cm, and giant hemangiomas are greater than 10 cm.
Hemangiomas may occur in various other regions of the body, such as the spinal cord, orbits, or vertebral bodies, but this article will focus on hepatic hemangiomas.
The etiology is not completely understood for hepatic hemangiomas. They sporadically occur without any known predisposing factors. When hemangiomas are greater than 10 cm, they are considered giant hemangiomas. Since they are considered vascular malformations, they enlarge by ectasia rather than hyperplasia or hypertrophy. In pregnancy, the hemangioma may grow secondary to the increase in hormones (estrogen and progesterone); however, estrogen receptors have not been proven in all tumors, and some tumors may even grow in the absence of estrogen therapy.
Several associated abnormalities include focal nodular hyperplasia of the liver and Kasabach-Merritt syndrome, which consists of multiple hemangiomas throughout the body, elevated fibrin degradation products, and thrombocytopenia.
Hepatic hemangiomas are five times more common in females than males. They can be seen in any age group, but the majority are diagnosed in those between the ages of 30 to 50 years (60 % to 80%). The prevalence may be higher, but since they are generally asymptomatic, they are not often diagnosed unless the patient is undergoing imaging of the abdomen for unrelated causes.
Microscopically, these appear as cavernous vascular spaces, hence the alternative name of cavernous hemangiomas. They are lined by endothelium and contain a fibrous stroma and blood products. In larger hemangiomas, a fibrous nodule or collagen scar may be seen.
Grossly, the lesions are a sponge-like consistency with a red to brown coloration. They are encased in a thin capsule and well circumscribed. They range from millimeters in size to some greater than 10 cm.
Generally, hepatic hemangiomas are asymptomatic and found in imaging studies for other reasons, for example, laparotomy or autopsy. Hemangiomas greater than 4 cm, however, tend to cause abdominal pain and discomfort.
The most common symptoms are right upper quadrant pain, generalized abdominal pain, or abdominal fullness. If there is bleeding within the lesion, this can lead to expansion and inflammation of Glisson’s capsule and lead to acute abdominal pain. When the hemangioma becomes large, symptomatology is related to compression of adjacent structures (i.e., early satiety from gastric compression).
Physical exam and laboratory testing are usually non-contributory. Rarely, there will be a palpable mass or changes in the liver functions tests.
Hepatic hemangiomas can be characterized, and diagnosis can be made by computed tomography (CT), magnetic resonance imaging (MRI), or ultrasound (US). It is important to note though, that multiple modalities are required for definitive diagnosis. Percutaneous biopsy is generally not recommended due to the risk of fatal hemorrhage. Diagnosis can be complicated further in the setting of cirrhosis or extra-hepatic malignancy. Thus additional testing/imaging may be required.
Imaging with ultrasound demonstrates a homogenous, well-defined, hyperechoic mass. If the patient has hepatic steatosis, the hemangioma may appear as hypoechoic. Color Doppler does not add additional diagnostic value. When lesions are larger than 5 cm, some heterogeneity may be demonstrated. Giant hemangiomas are lobulated, heterogeneous masses with a hyperechoic border. The imaging characteristics of hemangiomas on ultrasound are not diagnostic. Therefore, additional imaging is usually required.
On a non-contrasted CT, a hemangioma may appear as a well-circumscribed mass that is generally the same density or hypodense to blood vessels and liver. When large enough, there may be some heterogeneity and a low-density central scar. Calcifications are rarely seen.
Contrasted CT demonstrates 88% sensitivity and 84% to 98% specificity for the diagnosis of a hemangioma. On contrasted CT, the typical hemangioma demonstrates peripheral, discontinuous, nodular enhancement on arterial phase images with progressive centripetal filling on venous phase images. On delayed phase images, there is persistent complete filling. Giant hemangiomas follow a similar pattern. However, there may be a central scar, which does not fill/enhance.
Other variations include:
Atypical hemangiomas which may appear to enhance in a centrifugal pattern from the inside.
In the background of hepatic cirrhosis, the hemangioma may lose the characteristic enhancement pattern, and the flash-filling of small hemangioma can often mimic a hepatocellular carcinoma (HCC).
MRI is 90% sensitive and 91% to 99% specific for diagnosing hepatic hemangiomas. The typical hemangioma appears hypointense on T1-weighted images and hyperintense on T2-weight images. They are well-circumscribed and homogenous. On postcontrast imaging, the lesions demonstrate the typical peripheral, discontinuous, nodular enhancement with a delayed centripetal filling of the lesion, similar to that of CT. Smaller hemangiomas demonstrate flash-filling and again, may mimic HCC in the setting of hepatic cirrhosis.
Another modality that may be employed is the Technetium-99m pertechnetate-labeled red blood cell scan with single-photon emission CT (SPECT). There is similar sensitivity to that of MRI for lesions greater than 1 cm but has not been proven to have the same diagnostic value. Hemangiomas show hypoperfusion or a focal defect during the early dynamic scan with increased tracer uptake peaking approximately 30 to 50 minutes post-injection. The tracer remains within the lesion on delayed phase images. False negatives may occur secondary to fibrosis or thrombosis.
In asymptomatic patients, treatment is not necessary. Observation and long-term follow up may be a consideration; however, most patients do not require imaging follow up in lesions less than 5cm unless there is rapid growth or diagnosis is uncertain. As mentioned before, percutaneous biopsy is not indicated given the risk of hemorrhage.
In symptomatic patients or those with hemangiomas large enough causing mass effect, surgical resection should be considered after other causes of pain have been excluded. Surgical resection options are liver resection, hepatic artery ligation, enucleation, and in severe cases liver transplantation. Surgery is not entirely curative for symptoms, as it has been reported that 25% of those undergoing resection had persistence of symptoms.
Non-surgical treatment options include:
Cholangiocarcinomas demonstrate delayed persistent enhancement on CT and MRI; however, they tend to be heterogeneous on CT/MRI and less hyperintense on T2 weighted images. Additionally, they often invade and/or obstruct vasculature and bile ducts.
Hypervascular metastases should be considered in the setting of extra-hepatic malignancy. These tend to be multiple at the time of presentation and show contrast washout on delayed phase images.
Hepatic angiosarcomas also tend to be multiple at the time of presentation and will demonstrate vascular invasion and are more aggressive. These also tend to show contrast washout on delayed phase imaging. Lesions may also be present within the spleen.
Prognosis tends to be good. Complications may include spontaneous rupture or abscess formation, but are rarely seen.
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