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Difficulty: HardInterpreting Imaging Results

A 31-year-old nulliparous woman is evaluated in the emergency department for acute-onset right lower quadrant abdominal pain and nausea. Her only daily medication is a combined oral contraceptive pill, which she has taken for the past 10 years. Vital signs are within normal limits. Physical examination reveals localized tenderness in the right lower quadrant. A contrast-enhanced multiphasic CT scan of the abdomen and pelvis confirms early, uncomplicated acute appendicitis. Additionally, the radiologist reports an incidental 4.2-cm, well-demarcated, solid mass in the right hepatic lobe. On the arterial phase, the mass demonstrates intense, homogeneous enhancement, except for a central, star-shaped hypodense region. On the delayed portal venous phase, the bulk of the mass becomes isodense relative to the surrounding normal liver parenchyma, while the central star-shaped region demonstrates prominent contrast enhancement. Following appropriate surgical management of her appendicitis, which of the following is the most appropriate next step in the management of her incidental hepatic finding?

  1. Expectant management with no further targeted interventionAnswer
  2. B
    Immediate discontinuation of the oral contraceptive pills
  3. C
    Triphasic magnetic resonance imaging of the liver
  4. D
    Percutaneous core needle biopsy of the hepatic mass
  5. E
    Measurement of serum alpha-fetoprotein and cancer antigen 19-9 levels

Answer

Expectant management with no further targeted intervention
The correct action is expectant management with no further targeted intervention. The patient's CT scan provides a pathognomonic description of focal nodular hyperplasia (FNH). FNH is characterized on multiphasic CT by robust, homogeneous hyperenhancement during the arterial phase with a central hypodense stellate scar. Crucially, on the delayed venous phase, the mass becomes isodense to the liver, while the central scar retains contrast and becomes hyperdense. Because FNH is a benign hyperplastic response to a congenital vascular anomaly, it does not carry a risk for malignant transformation or spontaneous rupture. Therefore, it requires no surgical resection, no biopsy, and no specific imaging surveillance.

Step-by-Step Solution

1
Analyze the imaging characteristics described in the CT report.
The mass shows intense arterial enhancement and a central star-shaped scar that enhances on the delayed phase.
Accurate interpretation of multiphasic contrast enhancement patterns is crucial for differentiating hepatic masses.
2
Correlate the imaging findings with specific hepatic pathologies.
The pattern is classically pathognomonic for focal nodular hyperplasia (FNH).
While hepatic adenoma also enhances on arterial phase, it lacks the classically delayed-enhancing central stellate scar.
3
Determine the appropriate management for the established diagnosis.
Observation and expectant management without further testing or medication changes.
FNH is a benign vascular anomaly with virtually no risk of malignant transformation or hemorrhage, requiring no medical or surgical intervention.

Key Concept

Interpretation of multiphasic CT imaging to identify focal nodular hyperplasia (FNH) and subsequent expectant management.
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Topics

Interpreting Imaging Results

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