Hepatocellular adenoma

Section: Hepatobiliary Sub-section: Liver Curriculum: Curriculum, page 85

Definition

• Benign hepatic neoplasms in otherwise normal livers
• Hyperplastic hepatocytes
• Ability to undergo malignant transformation and/or cause intra-peritoneal haemorrhage

Epidemiology

• Rare
• Mostly women
• 20-40y
• Child bearing age
• OCP
• Increase in men due to obseity

Risk factors

• OCP (strong association)
• Obesity
• Anabolic steroid
• Metabolic disorders, e.g. diabetes or glycogen storage disease type I

Pathology

• Typically nodular with range of sizes.
• Uniform, although areas of congestion, necrosis, haemorrhage or fibrosis can be observed.
• Large subcapsular vessels and intratumoural fat.
• Microscopic
  • Tumoural monoclonal proliferation of well differentiated
  • Usually bland-looking hepatocytes arranged in sheets and cords that are usually 1-2 cells in width.

Molecular classification (Bordeaux classification) (Can mostly be determined from MRI):

• HNF1A (coding for hepatocyte nuclear factor 1a) inactivating mutations (30-40%)
  • On MRI have large amount of diffuse intratumoural fat
• Inflammatory adenomas (40-50%)
  • On MRI – hyperintense diffusely or peripherally (atoll sign) due to dilated sinusoids
• Β-catenin-mutated HCA (10-15%) – associated with higher risk of malignant transformation
• Unclassified HCAs (10%)

Clinical

• Mostly asymptomatic, incidental
• RUQ discomfort, fullness or pain due to mass
• Symptoms of intraperitoneal rupture – pain and hypovolaemic shock
  • Higher risk of rupture related to:
    • Size
    • Exophytic
    • Segment II & III (left sided)

Investigations

USS

• Often first detected by
• Hyperechoic – due to high lipid content
• Heterogeneic – due to haemorrhage, necrosis and fat content
• Colour doppler used to differentiate HCA from FNH CT
  • Degree of attenuation depends on composition of tumour and liver
  • May be hypoattenuating due to intratumoural fat, or isoattenuating relative to normal liver.
  • May be hyperattenuating in fatty liver.
  • May see peripheral enhancement due to large subcapsular feeding vessels. MRI
• usually heterogenous
• Bright on T1, hyperintense on T2.
• 1/3 have peripheral rim corresponding to fibrous capsule
• Well demarcated fat containing or haemorrhagic lesion. PET can be used if doubt.

Figure – MRI of adenoma. C – isointense on T1, D – heterogenous hypertense on T2.

Management

• Do NOT biopsy – risk of haemorrhage
• Risk of spontaneous haemorrhage, rupture and malignant transformation

Malignant potential

• < 5cm – unlikely to be malignant
• Risk of malignancy starts increasing after 5cm.

Indications for resection

• Adenomas in men (all adenomas in men should be considered for resection)

• 5cm in size in woman after cessation of hormonal therapy

• B-catenin mutated tumours (although in most cases you will not know this as biopsying hepatic adenomas is relatively risky)

Young woman with hepatic adenomas

• If a young woman has a hepatic adenoma while on the pill this should be discontinued as often this will result in shrinkage or resolution of the lesion.
• If the lesion returns to below 5cm – can continue with surveillance.
• Woman who are going to get pregnant need to be made aware that the adenoma may increase in size of have hemorrhagic complications.

AFP monitoring

• In

For acute haemorrhage

• hepatic arterial embolization can be effective for controlling bleeding, after which either resection or observation (with or without biopsy) could be considered.