Inflammatory hepatic adenoma

Inflammatory hepatic adenomas are a genetic and pathological subtype of hepatic adenoma. Their appearance and prognosis is different than other subtypes and they have the highest incidence of hemorrhage amongst hepatic adenoma subtypes.

Epidemiology

Inflammatory hepatic adenomas are the most common subtype of hepatic adenoma (40-50%) and occur most commonly in women with oral contraceptive pill (OCP) usage. They are also seen in older patients with hepatic steatosis or metabolic syndrome ⁶. They are therefore uncommon in young patients with no history of oral contraceptive usage.

Clinical presentation

Patients may present with fever, leukocytosis, elevated CRP, and elevated liver function tests (LFTs).

Radiographic features

MRI

• T1: isointense or mildly hyperintense relative to liver
• T1 C+ (Gd): ​marked arterial enhancement that fades in the portal venous phase and delayed phase
• T1 C+ (Eovist/Primovist)
  • unlike the other subtypes of adenomas, inflammatory adenomas can show enhancement after administration of hepatospecific contrast (although they do not contain liver cells or bile duct epithelium) ⁵; this occurs because inflammatory adenomas express OATP membrane receptors (where hepatospecific contrast molecules bind and normally present in cells derived from hepatocytes or bile duct epithelium)
  • the differential diagnosis of focal nodular hyperplasia can be tricky to distinguish, as both lesions show enhancement after administration of hepatospecific contrast (focal nodular hyperplasia enhances because it contains cells derived from hepatocytes and bile duct epithelium)
• IP/OP: no signal drop out on the out-of-phase sequence
• T2
  • ​usually hyperintense
  • an atoll sign may be seen: peripheral rim of high T2 signal intensity with the center of the lesion appearing isointense to the background liver; this is considered a characteristic sign

Treatment and prognosis

Inflammatory hepatic adenomas have a higher risk of bleeding than other subtypes (hemorrhage occurs in ~30% of this subtype). Adenomas >5 cm are also at increased risk of hemorrhage.

If an inflammatory hepatic adenoma is suspected on imaging, patients usually stop any oral contraceptive and the lesion regresses.

If the lesion does not regress, then one treatment pathway suggests:

• ≥5 cm: resection
• <5 cm: biopsy

Tissue diagnosis then confirms or changes the adenoma subtype. If inflammatory subtype is confirmed, management consists of:

• clinical and imaging follow up of any remaining adenomas until menopause
• resection or thermal ablation of enlarging adenomas that grow ≥5 cm

There is a very small risk that a hepatic adenoma may develop into a hepatocellular carcinoma (HCC).

Differential diagnosis

• other types of hepatic adenoma
  • HNF 1 alpha mutated hepatic adenoma
  • beta catenin mutated hepatic adenoma
  • unclassified hepatic adenoma
• hepatocellular carcinoma (HCC)
  • washout tends to leave the lesion hypointense compared to the rest of liver
  • different demographics
  • may be difficult to distinguish if well-differentiated
• focal nodular hyperplasia (FNH)
  • synonymous with the telangiectatic variant of focal nodular hyperplasia
  • there may be an overlap in appearance when using hepatospecific contrast e.g. Eovist ^4,5
• liver metastases (hypervascular) 
• for other differential considerations, see the main article: hepatic adenoma