From the RSNA refresher courses - Screening the cirrhotic liver for hepatocellular carcinoma with CT and MR imaging: Opportunities and pitfalls

The inherent distortion of the appearance of liver parenchyma by the underl ying pathologic changes of cirrhosis can obscure and simulate malignancy at imaging. That hepatocellular carcinoma is the most common abdominal malign ancy worldwide and occurs most often in patients with chronic liver disease and cirrhosis compounds this problem. Magnetic resonance (MR) imaging and, to a lesser extent, computed tomography (CT) can depict the underlying nod ular and fibrotic changes in patients with cirrhosis, particularly when sid erotic nodular regeneration is present. Application of state-of-the-art hel ical CT and MR imaging techniques has improved the ability to detect hepato cellular carcinoma in this population, but, even with these advances, fewer than 50% of small tumors are detected with either of these techniques in a screening population. Dynamic hepatic arterial-phase contrast material- en hanced imaging is essential with both CT and MR imaging to achieve even the se levels of success. Benign lesions that simulate tumor tissue are encount ered in many patients with cirrhosis and include focal fibrosis infarcted r egenerative nodules arteriovenous shunts he,,, mangiomas, pseudoaneurysms, and focal transient hepatic enhancement. An awareness of the imaging charac teristics of these lesions can help one avoid a mistaken diagnosis of hepat ocellular carcinoma in many cases.