Hi Emmanuel, HCC in the liver can take a variety of appearances on ultrasound. It is a manifestation of cirrhosis or hepatitis and it can present as a well defined solitary solid mass in the liver. It can also be multifocal mimicking metastatic disease and also may present as a diffuse process throughout the liver. Once it is present it can produce venous invasion and you may see tumour thrombus in the portal venous system. Personally I find ultrasound poor in terms of sensitivity, especially when there is background cirrhosis. The problem with cirrhosis is that you have fibrosis of the liver parenchyma and multiple often innumerable regenerating nodules all of which could potentially be a HCC deposit! We use ultrasound for surveillance and if a new nodule appears or the liver texture changes significantly between scans we use CT to clarify the situation. I think the use of serial ultrasound helps to increase our sensitivity as it provides a baseline study and then serial follow up scans. You could consider this similar to regular mammography surveillance for breast cancer screening.
Steve