Benign tumors of the liver include hepatic hemangioma, hepatocellular adenoma, focal nodular hyperplasia (FNH), and other less common lesions arising from hepatic epithelial or mesenchymal tissues (Table 44-1). Benign tumors of the liver may be found in up to 20% of the population,1 and are more than twice as common as malignant lesions. As a consequence of increased availability and utilization of abdominal computed tomography (CT) and magnetic resonance imaging (MRI), they are now being diagnosed with increasing frequency. Hemangiomas and FNH have an entirely benign natural history and therefore do not warrant resection; adenomas carry a risk of growth, hemorrhage, or malignant transformation and should be treated operatively. Correct identification of these lesions is therefore imperative, and establishment of a definitive diagnosis is often the primary challenge in managing this group of patients.
Table 44-1: Benign Tumors of the Liver |Favorite Table|Download (.pdf)
Table 44-1: Benign Tumors of the Liver
|Epithelial tumors||Hepatocellular||Focal nodular hyperplasia|
|Nodular regenerative hyperplasia|
|Bile duct||Bile duct adenoma|
|Bile duct cystadenoma|
|Mesenchymal tumors||Blood vessel||Hemangioma|
|Focal fatty infiltration|
Diagnostic uncertainty is common, and has been reported to be the indication for operation in as many as 40% of patients undergoing resection.2,3 Contemporary clinical, laboratory, and radiographic studies are often incapable of definitively distinguishing benign from malignant liver lesions. Symptoms, physical examination findings, and liver function tests are nonspecific. Tumor markers are normal in many patients with malignancy, and therefore should not be relied upon to identify a benign process. Hepatic ultrasonography is commonly employed, but often nonspecific. Currently, the most accurate radiographic modalities are CT and MRI. These are often complementary tests, and are usually diagnostic for hemangioma. MRI is becoming the diagnostic test of choice, with recent studies demonstrating an accuracy of 85–95%.4 CT and MRI have traditionally been less helpful in distinguishing adenoma from FNH,3,5 but recent advances in MRI contrast agents selectively excreted by hepatocytes suggest that use of such agents may permit reasonable differentiation of FNH, which retains contrast enhancement on delayed imaging, from adenoma, which does not.6Table 44-2 presents the MRI and CT characteristics of the more common benign lesions.
Table 44-2: Radiographic Features of Benign Tumors of the Liver |Favorite Table|Download (.pdf)
Table 44-2: Radiographic Features of Benign Tumors of the Liver
|Triphasic Contrast-Enhanced CT||MRI|
|Precontrast||Arterial Phase||Delayed Phase||T1||T2||Delayed Sequence|
|Hemangioma||Well-defined hypodensity||Peripheral nodular enhancement||Centripetal enhancement||Hypointense||Hyperintense||Centripetal enhancement|
|Focal nodular hyperplasia||Well-defined hypo/isodensity||Homogeneous enhancement||Increased scar uptake||Hypo/isointense||Isointense with possible increased scar signal||Retains gadobenate dimeglumine contrast enhancement|
|Hepatocellular adenoma||Isodensity; fat, hemorrhage or necrosis may be present||Homogeneous enhancement||Possible prolonged hyperdense enhancement||Mixed, may be hyperintense||Mixed, may be hyperintense||Does ...|
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