In a young to middle‑aged woman with an incidentally discovered focal nodular hyperplasia, what is the recommended diagnostic work‑up and management?

Focal Nodular Hyperplasia: Diagnostic Work-Up and Management

Direct Recommendation

In a young to middle-aged woman with incidentally discovered focal nodular hyperplasia, no intervention is required—conservative management with no routine follow-up imaging is appropriate once the diagnosis is confidently established by imaging alone. 1

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Diagnostic Strategy

Initial Characterization Based on Lesion Size

The diagnostic approach depends critically on lesion size at discovery:

• Lesions ≥1 cm: Proceed directly to multiphasic contrast-enhanced imaging (CT or MRI) to establish definitive diagnosis 2
• Lesions <1 cm: Perform short-interval ultrasound surveillance at ≤4-month intervals; if stable for 12 months, return to routine 6-month surveillance 2

Optimal Imaging Modalities

MRI is the most accurate imaging modality for FNH diagnosis, achieving 88-99% accuracy 2, and should be prioritized when available:

• MRI with hepatobiliary contrast (gadoxetate): FNH appears iso- or hyperintense on hepatobiliary phase, which is highly specific 2
• Multiphasic MRI with extracellular agents: Shows strong arterial enhancement with characteristic spoke-wheel pattern from central feeding artery 3
• Contrast-enhanced ultrasound (CEUS): Demonstrates strong hyperperfusion from large tortuous feeding artery in arterial phase, creating spoke-wheel appearance, with iso- or hyperechoic appearance in late phase 3, 2
• CT: Less sensitive than MRI but shows similar enhancement patterns; requires 2.5-5 mm slice thickness with arterial phase at 10-20 seconds post-injection 2

Pathognomonic Imaging Features

The diagnosis of FNH can be made confidently when these features are present:

• Arterial phase: Strong hyperperfusion from central feeding artery with centrifugal (spoke-wheel) filling pattern 3, 1
• Portal venous/late phase: Iso- or hyperechoic relative to surrounding liver (the "lightbulb" sign) 3
• Central scar: May be visible, particularly on MRI 3
• Hepatobiliary phase (gadoxetate MRI): Iso- or hyperintense uptake distinguishes FNH from adenoma 2

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When to Avoid Biopsy

Liver biopsy should be avoided as it is not necessary for diagnosis and carries bleeding risk 1. Biopsy is only indicated when:

• Imaging remains inconclusive after multiphasic contrast-enhanced studies 2
• Lesion lacks typical radiographic hallmarks preventing definitive diagnosis 2
• Lesion demonstrates growth or changing enhancement pattern during follow-up 2

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Management Approach

Conservative Management is Standard

Once FNH is confidently diagnosed by imaging, no surgical intervention or routine surveillance imaging is required 1, 4:

• FNH has an extremely low risk of spontaneous rupture, with only one case reported in literature 1
• Unlike hepatic adenomas, FNH does not require monitoring or intervention regardless of size 1
• Asymptomatic patients require only conservative clinical follow-up 4

Special Populations

Oral contraceptive use:

• Current guidelines do not consider oral contraceptive use causally related to FNH development or growth 1
• No need to discontinue oral contraceptives 1

Pregnancy considerations:

• Pregnancy is not contraindicated in women with FNH 1
• Vaginal delivery is not associated with increased risks 1
• Routine imaging surveillance is not recommended during pregnancy 1
• FNH size remains constant or decreases in most pregnant patients with no FNH-related complications 1

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Critical Differential Diagnoses

Hepatic Adenoma (Most Important to Exclude)

This is the most critical distinction because adenomas require different management:

• Adenoma features: Rapid peripheral-to-central enhancement in arterial phase, gradual washout in late phase, may show intralesional hemorrhage 3
• Key difference: Adenomas are hypointense on hepatobiliary phase of gadoxetate MRI, while FNH is iso/hyperintense 2
• Clinical significance: Adenomas carry significant rupture risk (especially during pregnancy) and require intervention if >5 cm 1

Hepatocellular Carcinoma

• HCC features: Arterial hyperenhancement with washout in portal venous or delayed phases 2
• Context matters: Consider patient's cirrhosis status and risk factors 3

Hypervascular Metastases

• Metastasis features: Peripheral ring enhancement (72% of cases) with hypoenhancement in late phase 2
• High specificity: Ring enhancement has 98% positive predictive value for malignancy 2

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Common Pitfalls and How to Avoid Them

Pitfall 1: Mistaking High-Flow Hemangioma for FNH

• Solution: Look carefully for peripheral nodular pattern in hemangiomas versus central spoke-wheel in FNH; use slow-motion review if needed 3

Pitfall 2: Confusing FNH with HCC in Nodular Liver

• Solution: FNH may be mistaken for HCC when liver appears nodular; always correlate with clinical context and hepatobiliary phase imaging 1

Pitfall 3: Missing Coexisting Lesions

• Solution: FNH coexists with other vascular hepatic lesions (like hemangiomas) in up to 20% of cases; evaluate entire liver 1

Pitfall 4: Late-Phase Washout in Older Patients

• Solution: FNH can show washout in late phase in patients >35 years due to bubble destruction or degenerative changes; don't automatically assume malignancy 3

Pitfall 5: Atypical/Non-Classical FNH

• Solution: Non-classical variants often lack central scar and typical architecture; when imaging is inconclusive despite optimal technique, proceed to biopsy rather than empiric surgery 2, 5

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Surgical Indications (Rare)

Surgery is indicated only in these specific scenarios:

• Symptomatic lesions: Persistent right upper quadrant or epigastric pain clearly attributable to FNH 5, 4
• Diagnostic uncertainty: When optimal imaging and biopsy remain inconclusive and malignancy cannot be excluded 6, 5
• Growing lesions with atypical features: Lesions demonstrating growth with imaging features not consistent with typical FNH 2

When surgery is performed, laparoscopic resection is feasible depending on anatomic location 6.