Imaging of hepatocellular carcinoma: practical guide to differential diagnosis.

Hepatocellular carcinoma (HCC) is most commonly seen in patients with cirrhosis. Criteria for diagnosis include arterial-phase enhancement, venous-phase washout, and a capsule on delayed sequences. Tiny HCC are best detected with magnetic resonance imaging using the new hepatocyte-specific gadolinium agents; otherwise, short-term follow up versus biopsy is considered. Diffuse HCC can be difficult to diagnose because of the inherent heterogeneous hepatic parenchyma in cirrhosis, however, portal vein expansion due to thrombosis is a helpful sign.