Focal nodular hyperplasia

Focal nodular hyperplasia (FNH)

• second most common benign liver lesion (second most common benign tumor of the liver after hemangiomas)
• etiopathology is not well understood, FNH may represent regeneration and hepatocellular proliferation after localised ischemic injury of the parenchyma or vascular malformation per se
• FNH is histologically characterized by nodular hyperplastic parenchyma surrounded by fibrous septa, central scar consists of connective tissue and malformed vessel
• very often an incidental finding
• often asymptomatic
• malignant degeneration of FNH has not been reported
• in some cases patients may have multiple FNH lesions
• FNH may be large (also as large as 10-20 cm in diameter)
• at imaging studies, typical feature of the FNS is central scar (abundant artery in connective tissue that divides into branches to form a star-shaped structure)
• diagnosis: Doppler US, CT, MR, biopsy in unclear cases
• US is often an initial imaging modality (CT or MR confirming the diagnosis)
• US features of FNH: there may be change in echogenicity, central scar, radiating septa within the lesion, color doppler may show a stellate flow signal within the lesion
• distinction between FNH and adenoma, hepatocellular carcinoma and metastases is critical
• FNH is not treated unless symptomatic