Imaging of Early Hepatocellular Carcinoma and Adenomatous Hyperplasia (Dysplastic Nodules) with Dynamic CT and a Combination of CT and Angiography: Experience with Resected Liver Specimens

Abstract

Early hepatocellular carcinoma (HCC) as defined by the Liver Cancer Study Group of Japan would correspond to high-grade dysplastic nodules with small foci of HCC in the majority of cases, using the classification system proposed by the International Working Party. A large number of early HCCs were revealed to be hypo- or isovascular in the arterial phase of dynamic CT. Only 5% of the lesions evaluated were hypervascular, which contrasted with advanced small HCCs, of which 94% were hypervascular. CT arterial portography (CTAP) showed hypoattenuation in 66% of early HCCs and isoattenuation in 34%. CT hepatic arteriography (CTHA) demonstrated hypoattenuation in 55% of early HCC, isoattenuation in 30% and hyperattenuation in 15%. These findings suggest that most early HCCs receive equal or reduced blood supply from both portal and arterial flow compared with surrounding noncancerous parenchyma. In contrast, 97% of small HCCs are hypoattenuated on CTAP, and 93% are hyperattenuated on CTHA. For nodule-in-nodule type HCC (advanced HCC within early HCC), the CT attenuation of the central and peripheral portions revealed areas of isolated advanced HCC and isolated early HCC, respectively. Adenomatous hyperplasia (low-grade dysplastic nodules) was not readily differentiated using the various imaging modalities, mainly due to the smaller size of these lesions compared to early HCC and/or a portal and arterial blood supply very similar to that of the surrounding parenchyma. Hemodynamic changes in cirrhotic liver were similarly evaluated using CTAP and CTHA, and the treatment of early HCC is briefly discussed herein.

A novel image‐guided surgery of hepatocellular carcinoma by indocyanine green fluorescence imaging navigation

“…Because most of small HCC nodules (<10 mm in diameter) are histologically well-differentiated [11], lack typical ultrasonographic patterns for HCC, and are not always hypervascular [12], it is sometimes very difficult to be diagnosed as HCC preoperatively. In fact, all of the new HCC nodules detected in this study were very small (<6 mm in diameter) and most of them were diagnosed as well-differentiated HCC.…”

Early Detection and Characterization of Hepatocellular Carcinoma: Value of Imaging Multistep Human Hepatocarcinogenesis

“…Angiography is not always effi cient in demonstrating arterial hypovascularity or portal venous fl ow in small nodules less than 1.5 cm in diameter, as previously reported [8][9][10][11] . Rather, US angiography and CTHA are more informative in detecting intranodular arterial vascularity.…”

“…It is widely known that some well-differentiated HCCs in an early stage are fed by the portal vein and not by the hepatic artery, unlike typical HCCs ( fi g. 2 ) [2,6,8,11,[24][25][26] . Therefore, some hypovascular HCCs (early-stage HCCs) show no perfusion defects on CTAP and may look like benign nodules with 'benign-appearing' patterns of the vasculature [27] .…”

Differentiation of early hepatocellular carcinoma from benign hepatocellular nodules on gadoxetic acid-enhanced MRI

“…These lesions are often hypovascular and lack arterial enhancement or a washout pattern [5,6]; thus, in dynamic contrastenhanced studies, they may show similar imaging findings to those of benign hepatocellular nodules of cirrhotic liver, such as dysplastic nodules.…”