Benign liver lesions

From most to least common

Haemangioma

• See separate topic

Focal nodular hyperplasia

• Epidemiology
  • Second most common benign liver lesion
  • Overwhelming majority are unifocal
  • Most <5cm
  • Most common in women 20-50
  • Minimal association with OCPs, if at all
• Aetiology
  • Unknown
  • Theorised to result from a developmental vascular malformation
• Pathophysiology
  • Polyclonal proliferation of normal liver parenchyma/hepatocytes in response to a fibrous scar or vessels found in the centre. Atypical biliary epithelium can be found scattered throughout the lesion. The central scar often contains a large artery that branches out into multiple smaller arteries in a spoke wheel pattern.
  • No malignant potential
  • Presence of Kupffer cells and biliary ductal cells can distinguish from adenoma
• Presentation
  • Mostly incidental finding on imaging or at surgery
  • Can cause vague symptoms, most commonly vague pain
  • Normal AFP levels
• Diagnosis
  • CT:
    • Central fibrous scar with radiating septa
    • 15% don't have a central scar
    • Strong hypervascularity in the arterial phase, with central non-enhancing scar
    • Iso-intense to liver in PV and delayed phases
  • Diagnosis based on imaging is harder when there is no central scar. Can be especially hard to differentiate from fibrolamellar HCC.
  • FNA has been recommended in certain cases but is often unrevealing
• Complications
  • Tiny risk of rupture or haemorrhage
  • Never been reported to transform into malignancy
• Management
  • Indications for removal: diagnostic uncertainty, symptoms
  • Surgery is very rarely necessary
  • Routine surveillance in asymptomatic patients but won't need much surveillance
  • Can grow very slowly, like 1mm per year, without raising any red flags
  • What to do with OCPs is controversial

Hepatic adenoma

• Benign proliferation of hepatocytes in the context of a normal liver
• Epidemiology
  • Rare
  • Unifocal in 70-88% of cases
    • >10 adenomas is described as liver adenomatosis (not usually associated with OCP use)
  • Mostly young women of child-bearing age (F:M 11:1)
  • Main risk factor is OCP use, after as short as 6 months of use
  • Sporadically associated with anabolic steroids/long-term pred
  • Also seen in glycogen storage disease types I and III and FAP
• Pathophysiology
  • Cords of benign hepatocytes containing increased glycogen and fat, with abnormal architecture (no bile ductules)
  • Haemorrhage and necrosis commonly seen
  • Can be divided into subtypes, including beta-catenin mutated adenoma, HNF1A mutated adenoma, inflammatory adenoma, and not otherwise specified adenoma
    • Beta-catenin adenomas have the highest risk of malignant transformation
  • Small potential for HCC transformation - 4.2%, with majority aoccurring in adenomas >5cm
  • AFP helpful in determining malignancy
  • Four subtypes of adenoma
• Presentation
  • Asymptomatic 25-50% of the time
  • Can cause upper abdominal pain - may be related to haemorrhage into the tumour or local compression
  • Mostly found as incidental findings on CT
  • Normal tumour markers
• Complications
  • Spontaneous rupture/haemorrhage - can lead to uncontrolled intraperitoneal bleeding
    • Doesn't occur in lesions <5cm
    • Active/life-threatening bleeding: hepatic artery embolisation, if possible, then semi-elective resection. If haemodynamically unstable, probably need theatre.
  • Malignant transformation
    • True risk is probably low, especially in lesions <5cm
• Imaging
  • See 'liver lesions' under radiology
  • Imaging findings are quite specific
  • Kupffer cell scan is a nuclear medicine study which can help to diagnose - not done much any more
• Management
  • Asymptomatic adenoma <5cm: cease OCP or anabolic steroids. Mostly leads to shrinking, but not complete regression. Can still increase in size or rupture after cessation of OCP.
  • Growth of adenoma off OCP, adenoma >5cm, adenoma in a man, or symptomatic: surgical resection.
    • Mostly need formal oncologic resection, but this is guided by individual factors.
    • For asymptomatic adenoma >5cm in a woman on OCP, stopping OCP and reviewing in 12 months is also an option
  • RFA may be possible for small/multiple adenomas not amenable to surgery.
  • Pre-pregnancy resection can be considered, as behaviour during pregnancy is unpredictable
  • Liver transplant has been performed for aggressive adenomatosis

Simple cyst

• See separate topic

Rare lesions

• Macroregenerative nodules (adenomatous hyperplasia)
  • Single or multiple
  • Well-circumscribed
  • Bile-stained, bulging surface nodules
  • Occur primarily in cirrhotics
  • Result from the hyperplastic response to chronic liver injury
  • Have malignant potential
• Nodular regenerative hyperplasia
  • Benign diffuse micronodularity (<2cm)
  • Associated with lymphoproliferative disorders, collagen vascular diseases, and the use of steroids or chemotherapy
  • No malignant potential and not associated with cirrhosis
  • Biopsy may be necessary
• Mesenchymal hamartomas
  • Rare solitary tumours of childhood
  • Usually large cystic masses found in the right liver
  • Present as progressive, painless, lesions with abdominal distension
  • Resection may be necessary with mass effect
• Fatty tumours of the liver
  • Primary lipomas
  • Myelolipomas
  • Angiolipomas
  • Angiomyolipomas