Description
Hepatic haemangiomas, are benign congenital vascular anomalies, typically non-symptomatic and discovered incidentally on imaging studies. They constitute the most common benign hepatic lesions and represent the most frequent tumours of the liver.
Pathogenesis
These lesions are considered congenital vascular malformations rather than true neoplasms, caused by an abnormal dilatation of the hepatic vascular system during embryogenesis. They are not associated with any risk of malignant transformation.
Epidemiology, Risk Factors & Associations
- Liver haemangiomas are typically seen in adults (0.4-20% of population), with an increased prevalence in females (F:M = 5:1).
- There is no known association with any particular ethnicity or geographical distribution.
- No clear genetic predisposition is known.
- They can be solitary or multiple, with the latter form, referred to as cavernous haemangiomatosis, being relatively rare.
- Although typically associated with hepatic adenomas, interval growth in size and number of haemangiomas has also been associated with exogenous estrogen and high-estrogen states (e.g., pregnancy). Regression occurs with reduction of circulating estrogen levels.
Clinical Features
- Liver haemangiomas are usually asymptomatic.
- Large lesions may cause abdominal discomfort or fullness, nausea, or vomiting due to mass effect.
- Rarely, a giant haemangioma can present with consumptive coagulopathy known as the Kasabach-Merritt syndrome.
Complications
The vast majority of hepatic haemangiomas are benign and cause no symptoms or complications. Rarely, complications such as rupture, intralesional bleeding, or obstructive jaundice may occur.
Subtypes
- Typical hepatic haemangioma – Most common benign liver tumour, usually asymptomatic.
- Atypical hepatic haemangioma
- Flash-filling hepatic haemangioma – Mimics hypervascular metastases; need careful evaluation to avoid misdiagnosis.
- Giant hepatic haemangioma – Higher risk of complications such as rupture, haemorrhage, and may cause symptoms due to mass effect.
- Other rare atypical features include:
- Capsular retraction
- Surrounding regional nodule hyperplasia
- Fatty infiltration
- Pedunculated hepatic haemangioma
- Cytic hepatic haemangioma
- Fluid-fluid level containing hepatic haemangioma
Hepatic Haemangioma
Flash Filling Hepatic Haemangioma
- Appearance:
- Relevance:
Calcified Hepatic Haemangioma
- Appearance: Presence of calcifications within the haemangioma, seen as hyperdense areas on CT.
- Relevance: Often associated with older haemangiomas; may indicate prior haemorrhage or thrombosis.
Hyalinised/Sclerosed Hepatic Haemangioma
- Appearance: Shows fibrosis and loss of typical vascular spaces, appears hypoechoic or isodense without typical enhancement.
- Relevance: Mimics fibrotic or necrotic tumours; difficult to diagnose without histology.
Other Unusual Imaging Patterns
- Appearance: Variants that do not fit typical or atypical patterns, including variations in size, shape, and enhancement.
- Relevance: Requires high index of suspicion and often additional imaging or follow-up.
Hepatic Haemangioma with Capsular Retraction
- Appearance: Localized retraction of the liver capsule overlying the haemangioma.
- Relevance: Uncommon; may be mistaken for malignancy; requires careful correlation with clinical and imaging findings.
Hepatic Haemangioma with Surrounding Regional Nodular Hyperplasia
- Appearance: Nodular hyperplasia adjacent to haemangioma, which enhances similarly to normal liver tissue.
- Relevance: May indicate increased local blood flow; requires differentiation from focal nodular hyperplasia.
Hepatic Haemangioma with Fatty Infiltration
- Appearance: Areas of fat within or surrounding the haemangioma, seen as hyperechoic areas on ultrasound.
- Relevance: Rare, but can complicate imaging interpretation; usually benign.
Pedunculated Hepatic Haemangioma
- Appearance: Haemangioma attached to the liver by a stalk, appearing as an exophytic mass.
- Relevance: May be confused with extrahepatic masses; requires careful imaging to confirm origin.
Cystic Hepatic Haemangioma
- Appearance: Contains cystic components, appearing as mixed echogenicity on ultrasound or mixed density on CT.
- Relevance: Rare and may be mistaken for cystic neoplasms or abscesses.
Fluid-Fluid Level Containing Hepatic Haemangioma
- Appearance: Shows fluid-fluid levels due to haemorrhage or thrombosis within the haemangioma.
- Relevance: Extremely rare, indicating previous internal bleeding or necrosis.
Summary
Hepatic haemangiomas present with a variety of imaging characteristics that can overlap with other liver pathologies. Accurate diagnosis often requires a combination of imaging techniques and clinical correlation to avoid misdiagnosis and unnecessary interventions.
Pathological Features
Morphology
- Macroscopically, they are well-defined, red-blue, spongy masses that can range in size from millimetres to more than 10 cm.
- Microscopically, they consist of large, blood-filled vascular spaces lined by a single layer of flat endothelial cells.
Histopathology
- Histologically, they show a characteristic pattern of large, cavernous vascular channels filled with blood and lined by a single layer of endothelial cells.
- There are typically no significant inflammatory infiltrates.
Radiological Features
General Features
- Usually well-defined, homogeneous lesions, found anywhere within the hepatic parenchyma.
- Small haemangiomas are typically homogeneous, while larger ones can show areas of central necrosis or fibrosis.
- Flash-filling haemangiomas demonstrate rapid, intense and homogenous enhancement on arterial phase imaging which persists in the portal venous phase without washout.
- Calcifications are rare.
CT
- Non-contrast CT: typically hypo- to isodense (<20 HU) compared to the liver.
- Arterial Phase: Peripheral, discontinuous, nodular enhancement
- Portal Venous Phase: Progressive centripetal fill-in.
- Delayed Phase: Further irregular fill-in. May be iso- or hyperattenuating to liver.
MRI
- T1: Hypointense compared to the liver.
- T2: Characteristically light bulb bright hyperintensity (less than CSF intensity or hepatic cyst)
- T2 FS: Increases in signal compared to T2
- T1 C+ (Gd): Similar to CT, shows peripheral nodular enhancement in the arterial phase with centripetal progression. Retains contrasts on delayed (> 5 min) phases.
- T1 C+ (Hepatobiliary): Variable appearances, therefore not useful
Ultrasound
- B-mode:
- Typically appears as a well-defined, homogenous, hyperechoic masses with posterior acoustic enhancement.
- May appear hypoechoic in the context of hepatic steatosis with an echogenic background.
- May appear hyperechoic at the periphery, and hypoechoic in the centre (reverse target sign)
- Colour Doppler: May show peripheral feeding vessels but no flow demonstrated within lesion itself.
- Contrast-enhanced: Using microbubble contrast agents (gas-filled microspheres with a lipid or protein shell)
- Arterial phase: Peripheral discontinuous globular enhancement
- Portal venous and late equilibrium phase: Progressive centripetal contrast filling and iso- or hyperenhancement
Differential Diagnosis
Imaging-based
General considerations for common hypervascular liver lesions (i.e. enhance in the late arterial phase):
- Focal nodular hyperplasia (FNH): The lesion is stealthy (isotense) on T1/T2 and homogenously hyperintense on arterial phase imaging, and it blends in with liver parenchyma on portal venous phase imaging, unlike haemangiomas which maintain their hyperintensity throughout. FNH also usually enhances on the hepatobiliary phase of gadoxetate-enhanced MRI, a feature not seen with haemangiomas. FNH often displays a T2 bright central scar that enhances late on contrast-enhanced MRI (and CT).
- Hepatic adenoma: Tends to be homogeneously hypervascular with areas of fat and/or haemorrhage. On portal venous and delayed phases, they are usually similar to background parenchyma. Signal drop demonstrated on out-of-phase MRI due to fat. Tends to favour right hepatic lobe.
- Hepatocellular carcinoma (HCC): HCC typically presents in the setting of chronic liver disease or cirrhosis and is often associated with elevated serum alpha-fetoprotein levels. On imaging, HCCs are often heterogeneously enhancing with areas of necrosis and demonstrate a pattern of arterial enhancement and portal venous or delayed phase washout, whereas haemangiomas demonstrate persistent enhancement.
- Hypervascular metastatic disease: Typical primaries include: renal cell carcinoma, thyroid carcinoma, neuroendocrine tumours, melanoma, leiomyosarocma, choriocarcinoma and breast cancer.
Management
- Management is typically conservative given the benign nature of these lesions.
- Intervention is rarely required but can be considered in symptomatic cases or if there is doubt about the diagnosis.
- If intervention is needed, options include surgical resection, radiofrequency ablation, or arterial embolisation.
- Referral is typically to a hepatologist or a liver surgeon.