Focal Nodular Hyperplasia Vs Hepatic Adenoma
Why Differentiate Liver Lesions?
Focal nodular hyperplasia (FNH) and hepatic adenoma (HA) are the common non-vascular benign liver tumors. Due to the advent of high-resolution imaging techniques, these lesions are detectable.
Lesions in the liver require proper diagnosis. Distinguishing various types of benign liver lesions helps in framing the appropriate treatment strategy. Most of the benign liver lesions are asymptomatic and in approximately one-third of the patients, abdominal pain or right upper quadrant discomfort is seen.
Salient Features of Focal Nodular Hyperplasia (FNH)
FNH is the second most common benign hepatic tumor in adults, and the third most common of all pediatric liver tumors.
FNH is 3 to 10 times more common than hepatic adenoma.
FNH is caused by arterial malformations within the liver. These malformations, coupled with changes in perfusion, cause a regenerative, hyperplastic response of the normal hepatocyte.
FNH is truly a benign condition and the chances of bleeding and malignant transformation are not expected to happen.
The prevalence of FNH was identified in families with hereditary hemorrhagic telangiectasia (HHT), an autosomal dominant genetic disorder.
Any comorbid conditions that cause a predisposition to the development of arterial malformations can increase the risk of FNH.
Molecular analysis revealed that β-Catenin is regarded as a pivotal stimulus for the proliferation of hepatocytes, liver development, and liver regeneration after injury.
The most sensitive technique to detect FNH is MRI which has the highest sensitivity and specificity.
Most cases of FNH do not require any treatment. In rare cases, surgical interventions are necessary.
Salient Features of Hepatic Adenomas
Liver, Credits: pixabay
HA is the third most common benign neoplasm.
Hepatic adenomas are commonly seen in females who use oral contraceptives.
The major risk factor for the development of HA is exposure to estrogenic or androgenic steroids.
HA is reported to be approximately 3–10 times less common than FNH.
HA contains no bile ducts or ductular structures.
The clinical features of HA include abdominal pain, abdominal mass, intraperitoneal hemorrhage, and abnormal liver tests.
When 10 or more adenomas are seen, the condition is called adenomatosis.
Molecular analysis revealed that mutations in the genes of hepatocyte nuclear factor 1α (HNF-1α) in 40–50% of cases and β-catenin in <10% of cases.
Major complications of HA include hemorrhage and malignant transformation. Clinically significant hemorrhage is observed in 20–25% of cases.
CT and MRI scans are used to diagnose hepatic adenomas.
The table below describes the differences between focal nodular hyperplasia and hepatic adenomaFNHHepatic adenomaTypical patientAll ages2nd to 5th decadeGender biasFemale>MaleNearly exclusively femalePrevalence>18 years4-30/1000Unreliable data, very lowPrevalence<18 years0.2/1000Unreliable data, very lowClinical presentationAsymptomaticAbdominal pain or asymptomaticLaboratory parametersNormal or non-remarkable
Normal AFP
Normal or non-remarkable
Normal AFP
ImagingSpokes of wheel vascular patternCircular vascular pattern around the lesionPathological MechanismsHyperplastic reaction to vascular abnormalityUncontrolled growth
Possibly estrogen-inducedHistopathological featuresCentral scar
Ductular reaction
Fibrosis
Liver cell plates
No bile ducts
No fibrosisMutational analysisPolyclonalMonoclonalGene expressionBeta-catenin pathway activation
Ang-1/Ang-2 mRNA ratio elevatedHNF-1 alpha inactivation
Beta-catenin pathway activation
Ang-1/Ang-2 mRNA ratio normalComplicationsNoneBleeding
Hepatocellular carcinomaTreatment of choiceClassic FNH: expectative
Diagnosis doubtful: consider excisionWithdrawal of estrogen treatment
Excision/partial liver resection
Adapted from https://www.karger.com/Article/Fulltext/268404, accessed on 07/10/20
Take-Home Message
A clear understanding of benign liver lesions may help physicians to plan appropriate treatment regimens.