Diagnosis and treatment of focal nodular hyperplasia

Focal nodular hyperplasia is an uncommon, benign lesion of the liver of minimal clinical significance. Its importance lies in differentiating it from clinically significant lesions such as liver cell adenoma and hepatocellular carcinoma. The purpose of this review is to provide a background on the pathogenesis of focal nodular hyperplasia, discuss current imaging modalities which provide the most specificity in diagnosis, and provide an update on the accepted management of these lesions. While debate still exists, most current authors believe that focal nodular hyperplasia represents a local response of the liver to injury. The source of that injury seems to be vascular malformations. Magnetic resonance imaging (MRI) provides the most specificity in diagnosis, although the characteristics are still being described. Classically, the lesions will be isointense on T2-weighted images with rapid homogenous contrast enhancement and delayed enhancing central stellate scar. Surgical resection is limited to symptomatic lesions or lesions with atypical imaging characteristics suggesting the possibility of a malignant diagnosis. Percutaneous biopsy can be helpful in those lesions where there is an overall high suspicion of focal nodular hyperplasia, but some of the clinical aspects or imaging characteristics are atypical for the diagnosis. The use of embolization as first line therapy for symptomatic lesions deserves further investigation.