Hepatic focal nodular hyperplasia: The "star sign" on gadolinium-enhanced magnetic resonance angiography

Background/Aims: This study aimed at presenting the three-dimensional gadolinium-enhanced magnetic resonance angiography findings of hepatic focal nodular hyperplasia with angiographic correlation. Methodology: Three patients (one had abdominal pain, two were asymptomatic) with liver mass or nodules in the liver revealed on ultrasound underwent three-dimensional gadolinium-enhanced magnetic resonance angiography. Catheter angiography was available for correlation in all three cases. Other imaging studies including conventional magnetic resonance imaging in three patients, computed tomography in two and scintigraphy scan in one were reviewed. Surgical resection and biopsy were performed in one and two patients respectively. Results: The ultrasound, computed tomography, magnetic resonance and scintigraphy findings were non-specific for focal nodular hyperplasia in all three patients. However, gadolinium-enhanced magnetic resonance angiography demonstrated tumor vessels radiating from its center to the periphery, which corresponded to the spokes of the characteristic "spokewheel" pattern on catheter angiography, producing the so called "star sign," that may suggest the diagnosis of focal nodular hyperplasia. Histopathologic examinations revealed focal nodular hyperplasia. Conclusions: This report highlights the usefulness of gadolinium-enhanced magnetic resonance angiography in the diagnosis of hepatic focal nodular hyperplasia by demonstrating the "star sign" and that computed tomography, scintigraphy, and catheter angiography may thus be obviated in such instances.