Examkin

Question

Difficulty: Very hardInterpreting Imaging Results

A 28-year-old woman presents to the ambulatory care clinic for evaluation of vague, intermittent right upper quadrant abdominal discomfort that has been present for the past three months. She has no significant past medical history other than a 10-year history of taking combined oral contraceptive pills. Vital signs are within normal limits, and physical examination reveals a soft, non-tender abdomen with no palpable hepatomegaly. Laboratory studies, including liver function tests, basic metabolic panel, alpha-fetoprotein, and CA 19-9, are all within normal limits. Given her persistent symptoms, a multiphasic contrast-enhanced magnetic resonance imaging (MRI) of the liver is performed. The MRI reveals a solitary, 6-cm, well-demarcated lesion in the right hepatic lobe. During the arterial phase, the lesion demonstrates robust, homogeneous hyperenhancement. On the portal venous and delayed phases, the lesion becomes isointense to the surrounding normal liver parenchyma. A central stellate structure is identified within the lesion; this structure is hyperintense on T2-weighted sequences and demonstrates progressive contrast enhancement on the delayed phase. Based on the precise interpretation of these imaging findings, which of the following is the most appropriate next step in management?

  1. Reassurance and routine clinical observationAnswer
  2. B
    Discontinuation of oral contraceptives and serial ultrasound surveillance
  3. C
    Image-guided percutaneous core needle biopsy
  4. D
    Surgical resection of the hepatic lesion
  5. E
    Whole-body fluorodeoxyglucose positron emission tomography scan

Answer

Reassurance and routine clinical observation
The correct answer is reassurance and routine clinical observation. The patient's multiphasic MRI demonstrates classical features of focal nodular hyperplasia (FNH). FNH is characterized by robust, homogeneous arterial phase hyperenhancement and becomes isointense on portal venous and delayed phases. The hallmark distinguishing feature is the presence of a central stellate scar, which is typically hyperintense on T2-weighted imaging (due to vascularity, edema, and myxoid stroma) and demonstrates progressive, delayed contrast enhancement (due to the slow accumulation of contrast within the dense fibrous tissue of the scar). Although the patient has a long history of oral contraceptive use—a strong clinical distractor that frequently baits a diagnosis of hepatic adenoma—the precise imaging characteristics exclude an adenoma, which typically lacks a delayed-enhancing central scar. FNH is a benign hyperplastic response to a localized vascular anomaly with no malignant potential and an extremely low risk of complications such as hemorrhage. Therefore, for an incidentally found or mildly symptomatic FNH with definitive imaging features, the standard of care is conservative management without the need for medication cessation, invasive biopsy, or surgical resection.

Step-by-Step Solution

1
Analyze the clinical history and identify the diagnostic dilemma.
The patient is a young woman with a 10-year history of oral contraceptive use presenting with a large hepatic lesion. This strongly elevates clinical suspicion for a hepatic adenoma.
Recognizing risk factors is critical, but they must be carefully correlated with objective diagnostic data to avoid cognitive anchoring.
2
Interpret the specific multiphasic MRI findings provided in the stem.
The lesion shows homogeneous arterial hyperenhancement and becomes isointense on later phases. Crucially, it features a central stellate scar that is hyperintense on T2-weighted imaging and exhibits progressive, delayed contrast enhancement.
Multiphasic MRI is the gold standard for characterizing hepatic lesions. The enhancement pattern of the central scar is the defining discriminator between competing diagnoses.
3
Synthesize the imaging interpretation to establish a definitive diagnosis.
The combination of arterial hyperenhancement, isointensity on delayed phases, and a T2-hyperintense, delayed-enhancing central scar is pathognomonic for focal nodular hyperplasia (FNH).
Hepatic adenomas typically lack a central scar and show washout or isointensity on delayed phases without late central enhancement. Fibrolamellar hepatocellular carcinoma has a scar, but it is T2 hypointense and does not enhance on delayed imaging.
4
Determine the standard of care for the diagnosed condition.
Because FNH is a benign, non-neoplastic hyperplastic response to a localized vascular anomaly with virtually zero risk of malignant transformation or rupture, the standard management is reassurance and observation.
Applying the correct management protocol prevents unnecessary surgical interventions or unwarranted discontinuation of the patient's preferred contraceptive method.

Key Concept

Focal nodular hyperplasia (FNH) is characterized on MRI by a T2-hyperintense central scar that exhibits delayed contrast enhancement, distinguishing it from hepatic adenomas and fibrolamellar hepatocellular carcinomas; it is managed conservatively.
Estimated Time:1m 30s
Rate this question

Topics

Interpreting Imaging Results

More questions from this topic