Focal Nodular Hyperplasia

Focal nodular hyperplasia (FNH) is a benign hyperplastic hepatocellular response to a pre existing arterial malformation, forming a nodule with a central stellate scar.

• Second most common benign hepatic tumour (prevalence 0.4 to 3%), women aged 20 to 50 (8:1).
• Not caused by oral contraceptives, although oestrogen may increase lesion size.
• Polyclonal origin; no malignant potential; no haemorrhage.
• Associated with vascular anomalies (hepatic hemangioma, hereditary haemorrhagic telangiectasia) and chemotherapy survivors.
• Multiple lesions in 20%.

• Asymptomatic and incidental in over 80%.
• Rarely right upper quadrant discomfort, palpable mass.
• Normal liver tests; alpha fetoprotein normal.
• No complications such as rupture.

• Ultrasound: iso or hypoechoic lesion with spoke wheel vascularity on colour Doppler.
• Contrast CT/MRI: homogeneous arterial enhancement, isointense in portal and delayed phases, central scar hyperintense on T2 with delayed enhancement.
• MRI with gadoxetate (hepatobiliary agent): iso to hyperintense in hepatobiliary phase (specific, over 90%).
• Biopsy is rarely needed: for atypical lesions (no scar, heterogeneous), showing hyperplastic hepatocytes, abnormal arteries, ductular proliferation; glutamine synthetase map-like staining.
• Differential diagnosis: hepatic adenoma, fibrolamellar carcinoma, hepatocellular carcinoma, hypervascular metastases.

• Reassurance. No treatment is required for typical lesions.
• Oral contraceptives and hormone replacement can continue; pregnancy is safe.
• Imaging follow up at 6 to 12 months, and then only if symptomatic or atypical, then no further surveillance.
• Resection or ablation only for symptomatic lesions with significant pain, diagnostic uncertainty with atypical features, or rapid growth.
• Transarterial embolisation for symptomatic lesions that are not resectable.
• Avoid unnecessary surgery in typical cases.
• Discontinue androgen and anabolic steroids.