Findings: Image #1 is a noncontrasted enhanced CT image through the liver demonstrating an 8 x 6.5 cm. mass within the lateral segment of the left lobe of the liver. The mass is isodense with liver parenchyma.
Image #2 is a post contrast enhanced axial CT image through the same region of the liver demonstrating slightly increased enhancement relative to the remainder of the liver.
Image #3 is a sulfur colloid liver-spleen scan. The image demonstrates enlargement of the left lobe of the liver without evidence for abnormal uptake. No discrete mass is identified.
Diagnosis: Focal nodular hyperplasia (FNH).
Discussion: Focal nodular hyperplasia is a rare, benign disease characterized by a solid, nonencapsulated hepatic tumor consisting of nodules of hyperplastic hepatocyte. The vast majority of cases are incidentally discovered in the third to fifth decade of life. There is a female predominance. Lesions are usually solitary and patients are generally asymptomatic.
On unenhanced computed tomographic examinations, focal nodular hyperplasia is generally isodense or hypodense to normal liver parenchyma. The lesions are often detected as a subtle contour abnormality along the edge of the liver. In addition, the lesion may demonstrate a central hypodense internal scar. Post contrast enhanced images generally demonstrate relative hyperdensity in comparison to the surrounding normal liver parenchyma. Although the FNHappears relatively hyperdense during the arterial and early portal venous phase, the lesion often become isodense to the liver during the late portal venous phase. In addition, the central scar which is often seen in focal nodular hyperplasia may remain hyperdense during delayed imaging.
Sulfur colloid liver-spleen scans may be more specific for the diagnosis of focal nodular hyperplasia than computed tomography. Due to the fact that focal nodular hyperplasia demonstrates hyperplastic hepatocytes which contain Kupffer cells, these lesions normal concentrate sulfur colloid. For this reason, normal or slightly increased uptake by hepatic mass on sulfur colloid scan generally suggests the diagnosis of focal nodular hyperplasia.
References:
Kinnard M. Nuclear Imaging of Solid Hepatic Masses.
Seminars in Roentgenology. 1995;30(4)375-395.
Jacobs J. Computed Tomography Imaging of Focal Hepatic Lesions.
Seminars in Roentgenology 1995;30(4)308-323.
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