Table of Contents

Adenoma

Author: Bill H. Warren, MD

 

Synonyms

  • Hepatocellular adenoma
  • Liver cell adenoma
  • Telangiectatic/inflammatory adenoma (formerly telangiectatic FNH)

 

Epidemiology

  • Rare benign neoplasm, less common than FNH
  • More common in young women (ages 20-44), especially with prolonged oral contraceptive use
  • Incidence with oral contraceptives estimated 4/100.000 users
  • Female:male ratio 10:1
  • Pregnancy increases growth rate and risk of rupture
  • May decrease in size and decrease risk of rupture if oral contraceptives discontinued
  • Increased risk of rupture: size >5 cm and subcapsular location
  • Does not exist in cirrhosis

 

Etiology

  • Increased incidence with use of oral contraceptives and anabolic steroids
  • Hepatic steatosis associated with increased number and growth rate of adenomas
  • Multiple adenomas commonly seen in von Gierke type 1A glycogen storage disease
  • Increased incidence with diabetes mellitus

 

Pathology

  • Arises from hepatocytes
  • Recent genetic and pathologic studies have resulted in a new classification of adenomas that accounts for >90% of adenomas:   

3 subtypes:

  • Inflammatory / teleangiectatic (formerly "teleangiectatic FNH") hepatocellular adenoma—accounts for 40-50% of adenomas, associated with IL6ST gene, characterized by sinusoidal dilatation (i.e. intralesional peliosis), and prone to internal hemorrhage
  • HNF 1-a-mutated hepatocellular adenoma—accounts for 30-35% of adenomas and is characterized by diffuse internal steatosis
  • Beta-catenin-mutated hepatocellular adenoma—accounts for 10-15% of adenomas, increased frequency in men, with increased risk of development of hepatocellular carcinoma

 

  • May be mistaken clinically and pathologically for HCC
  • May degenerate into HCC, especially if >10 cm
  • Large size range (1-30 cm)
  • Usually single but may be multiple (adenomatosis)
  • Well circumscribed mass with fibrous pseudocapsule
  • Microscopically absence of portal and central veins and bile ducts, which distinguishes adenoma from FNH

 

Clinical Presentation

  • Typical presentation is young woman on oral contraceptive with right upper quadrant or epigastric pain secondary to hemorrhage
  • LFTs usually normal
  • Higher risk of rupture during pregnancy

 

Imaging Findings

General

  • Heterogeneous hypervascular mass with foci of fat and hemorrhage
  • May contain calcification or areas of necrosis
  • Most commonly subcapsular right lobe of liver (75%)
  • Intraparenchymal or pedunculated (10%)

 

CT

Unenhanced

  • Well-defined mass, usually isodense, may be hypodense from fat
  • Hemorrhage—subcapsular, intratumoral, or parenchymal
  • Fat and calcification less commonly seen

Arterial

heterogeneous hyperdense enhancement

Portal venous

hyper-, iso-, or hypodense to liver

Equilibrium

  • Generally homogeneously iso- or hypodense (washout)
  • May have hyperattenuated pseudocapsule
  • Larger lesions generally heterogeneously hypodense

MR

T1w

  • Heterogeneous signal intensity
  • Increased signal intensity secondary to fat and recent hemorrhage
  • Decreased signal intensity secondary to calcification and old hemorrhage
  • Hypointense fibrous pseudocapsule

T2w

  • Heterogeneous signal intensity
  • Increased signal intensity from old hemorrhage and necrosis
  • Decreased signal intensity from fat and recent hemorrhage
  • Hypointense fibrous pseudocapsule
  • Fat suppression distinguishes fat from hemorrhage

Opposed-phase GRE

Helpful to detect presence of fat

Arterial

heterogeneous enhancement

Delayed

typically heterogenerously hypointense (washout) with hyperintense pseudocapsule

Hepatospecific

  • Usually no uptake or retention of contrast agent—hypointense to liver
  • Best for differentiating from FNH, which will be iso- to hyperintense compared to liver

US

General

findings are non-specific

Gray-scale

  • Heterogeneous well-circumscribed mass that may be hyper- or hypoechoic
  • Heterogeneous appearance may be due to hemorrhage, fat, necrosis, or calcification

Color Doppler/contrast-enhanced US

  • Hypervascular mass
  • Large peripheral arteries and veins
  • May assist in making the distinction from FNH because of the appearance of intratumoral and peritumoral vessels in the absence of a central arterial signal (absence of spoke wheel artery)

 

Differential Diagnosis

  • Hepatocellular carcinoma (HCC) - May be identical to adenoma on imaging, especially well-differentiated
  • Fibrolamellar HCC - Usually large lobulated mass with central scar and septa
  • Focal nodular hyperplasia (FNH) - Homogeneous enhancement on arterial phase, central scar on T2, which enhances on delayed imaging, hyperintense with hepatospecific Gd contrast agents:
  • Hypervascular metastasis - Usually multiple, history of primary malignancy

 

Management

  • Asymptomatic lesions <5 cm—discontinue OCPs and re-image in 6 months
  • Lesions >5 cm and/or subcapsular location-surgical resection
  • Avoid pregnancy with known adenoma or consider prophylactic surgical resection prior to pregnancy because of unpredictable response during pregnancy
  • If discovered incidentally during pregnancy, plan surgical resection during second trimester for large or subcapsular lesions because of risk of spontaneous rupture

 

Bibliography

 

 

 

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