RESUMO
Hepatocellular carcinoma (HCC) is the most common primary malignancy of the liver with a high incidence worldwide and a high associated mortality. Well-recognized risk factors that cause a predisposition to the development of HCC include chronic infection with the hepatitis B or C virus, alcohol-related and non-alcohol-related fatty liver disease, and cirrhosis. In these chronically diseased livers, benign regenerative nodules can increase in size and develop cellular atypia that progress into dysplastic nodules and ultimately HCC. This sequence of hepatocarcinogenesis is coupled with changes in nodule vascularity, including progressive decreased density of portal triads and induced neoangiogenesis, resulting in increased hepatic arterial recruitment. Changes in vascularity result in an array of patterns of nodule enhancement and washout, which can be sensitively depicted with dynamic real-time contrast-enhanced US. Regenerative nodules are isoenhancing relative to the liver with all phases, while HCC classically shows avid arterial phase hyperenhancement with late mild washout. In between, there is great variation as nodules evolve through progressive grades of dysplasia toward HCC. Observed patterns of enhancement and washout can be used to diagnose or stratify the risk of malignancy in liver nodules by using the diagnostic algorithm described by the American College of Radiology Liver Imaging Reporting and Data System (LI-RADS). This facilitates the detection and close monitoring of potential early-stage disease. LI-RADS categorizes nodules according to a probabilistic likelihood for HCC with criteria for LR-5 nodules that are highly specific for the diagnosis of HCC, allowing treatment without exposing the patient to invasive biopsy. An invited commentary by Fetzer is available online. Online supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article. ©RSNA, 2022.