What is the recommended approach to surveillance for patients with focal nodular hyperplasia (FNH)?

Surveillance Approach for Focal Nodular Hyperplasia

Focal nodular hyperplasia (FNH) does not require routine monitoring or surveillance after diagnosis, as it has no malignant potential and rarely causes complications. 1

Diagnostic Characteristics of FNH

• FNH is the second most common benign liver tumor after hemangioma, with prevalence of 0.3% to 3% 1
• Predominantly affects reproductive-aged women 1, 2
• May coexist with other vascular hepatic lesions such as hepatic hemangiomas in up to 20% of cases 1

Imaging Features

• MRI has higher sensitivity and specificity for FNH than ultrasound or CT 2
• Typical MRI findings:
  • Iso- or hypointense on T1-weighted images
  • Slightly hyper- or isointense on T2-weighted images
  • Hyperintense central scar on T2-weighted images
  • Intense homogeneous enhancement during arterial phase
  • Enhancement of central scar during later phases 2

Evidence-Based Surveillance Recommendations

General Population

• No routine monitoring is required after diagnosis 1
• No follow-up imaging is necessary for asymptomatic FNH 1

During Pregnancy

• Pregnancy is not contraindicated in women with FNH 1
• No monitoring is required during pregnancy 1
• Vaginal delivery is not associated with increased risks 1

Management Approach

Asymptomatic FNH

• Conservative management is appropriate 2, 3
• No biopsy or surgery required for asymptomatic patients 2
• No evidence that FNH is premalignant 3

Symptomatic FNH

• Surgical intervention should be considered only if:
  • Patient has persistent upper abdominal pain attributed to FNH
  • Rapid growth is documented
  • Complications such as weight loss or portal compression occur (extremely rare) 3, 4

Special Considerations

Contrast with Other Benign Liver Lesions

• Unlike hepatocellular adenomas (HCAs), which require monitoring during pregnancy if >5 cm, FNH does not require monitoring regardless of size 1
• Unlike hemangiomas >5 cm, which may benefit from surveillance during pregnancy, FNH requires no special monitoring 1, 5

Common Pitfalls to Avoid

1. Misdiagnosing FNH as hepatocellular adenoma, hepatocellular carcinoma, or hypervascular metastasis 2, 6
2. Performing unnecessary biopsies or resections for asymptomatic FNH 2, 3
3. Implementing unnecessary surveillance protocols that are appropriate for other liver lesions but not for FNH 1

In conclusion, the evidence consistently shows that FNH is a benign condition that does not require routine surveillance after diagnosis, even during pregnancy, unless the patient develops symptoms or shows rapid growth.