Focal lesions in cirrhosis: Not always HCC

- A wide spectrum of benign and malignant tumors and pseudolesions may be found in cirrhotic livers, aside from HCC.
- MRI is the best imaging technique because it provides a complementary approach with both morphological and quantitative imaging.
- Hepatospecific MR contrast agents, especially gadoxetic acid, notwithstanding their diagnostic value, may lead to several pitfalls, mainly to over-diagnosis of HCC.
- Other MR sequences, available CT or US, and liver biopsy, enable diagnosis in the majority of patients.

Even though most hepatocellular carcinomas (HCC) develop in the setting of cirrhosis, numerous other focal liver lesions and pseudolesions may be encountered. The role of the radiologist is therefore to differentiate these lesions from HCC to avoid under- and overdiagnosis. There are several ways of classifying these lesions: those which predate the development of fibrosis and cirrhosis (cystic lesions, hemangioma), those related to or a consequence of cirrhosis (regenerative nodules, dysplastic nodules, focal fibrosis, peribiliary cysts, shunts, or even cholangiocarcinoma), and those related to the underlying cause of chronic liver disease (lymphoma). Finally, some may develop independently (liver metastases). From an imaging point of view, it is important to remember that the imaging features of pre-existing lesions are not dramatically changed by cirrhosis. Differentiating non-HCC from HCC requires not only an understanding of the multi-step process of hepatocarcinogenesis, but also the importance of medical history, and of complimentary imaging modalities, namely computed tomography (CT) and magnetic resonance imaging (MRI). This review article gives an overview of the imaging features of benign and malignant non-HCC focal liver lesions in the setting of cirrhosis, with a focus on CT and MR imaging.