An overview of hepatocellular carcinoma with atypical enhancement pattern: spectrum of magnetic resonance imaging findings with pathologic correlation

Abstract

Background: In the setting of cirrhotic liver, the diagnosis of hepatocellular carcinoma (HCC) is straightforward when typical imaging findings consisting of arterial hypervascularity followed by portal-venous washout are present in nodules larger than 1 cm. However, due to the complexity of hepatocarcinogenesis, not all HCCs present with typical vascular behaviour. Atypical forms such as hypervascular HCC without washout, isovascular or even hypovascular HCC can pose diagnostic dilemmas. In such cases, it is important to consider also the appearance of the nodules on diffusion-weighted imaging and hepatobiliary phase. In this regard, diffusion restriction and hypointensity on hepatobiliary phase are suggestive of malignancy. If both findings are present in hypervascular lesion without washout, or even in iso- or hypovascular lesion in cirrhotic liver, HCC should be considered. Moreover, other ancillary imaging findings such as the presence of the capsule, fat content, signal intensity on T2-weighted image favour the diagnosis of HCC. Another form of atypical HCCs are lesions which show hyperintensity on hepatobiliary phase. Therefore, the aim of the present study was to provide an overview of HCCs with atypical enhancement pattern, and focus on their magnetic resonance imaging (MRI) features.

Conclusions: In order to correctly characterize atypical HCC lesions in cirrhotic liver it is important to consider not only vascular behaviour of the nodule, but also ancillary MRI features, such as diffusion restriction, hepatobiliary phase hypointensity, and T2-weighted hyperintensity. Fat content, corona enhancement, mosaic architecture are other MRI feautures which favour the diagnosis of HCC even in the absence of typical vascular profile.

Keywords: diffusion magnetic resonance imaging; hepatocellular carcinoma; liver cirrhosis; magnetic resonance imaging.

Figure 1

Hypovascular hepatocellular carcinoma (HCC) in 58-year old woman with cirrhosis. On axial T2-weighted image (A), diffusion-weighted image (B) and on in-phase image (C) tumor is isointense with surrounding liver parenchyma. On opposed-phase image there is a partial drop of signal intensity in the lesion (arrow) corresponding to the fatty component (D). The lesion (arrow) is slightly hypointense on arterial phase (E), while it is clearly hypovascular on portal-venous phase (F). On hepatobiliary phase after administration of gadoxetic acid the lesion (arrow) is hypointense (G). Hematoxylin and eosin (H&E) staining showed well-differentiated HCC with fat deposition; original magnification x 200 (H).

Figure 2

Isovascular hepatocellular carcinoma (HCC) in 55-year old woman with cirrhosis. On T2-weighted image slightly hyperintense nodule (arrow) is seen in liver segment VII (A). No lesion is seen on arterial (B) and portal venous phase (C). On hepatobiliary phase after administration of gadoxetic acid the lesion (arrow) is hypointense (D). Diffusion-weighted image shows diffusion restriction of the lesion (arrow) (E). Hematoxylin and eosin (H&E) staining showed well-differentiated HCC; original magnification x 200 (F).

Figure 3

Hypervascular hepatocellular carcinoma (HCC) without washout in 64-year old man with cirrhosis. Axial T2-weighted fat-suppressed image shows hyperintense nodule (arrow) in liver segment VIII (A). On arterial phase the nodule (arrow) is hypervascular (B) without washout on portal-venous phase (C). On hepatobiliary phase the nodule (arrow) is hypointense (D) and on diffusion-weighted image it is hyperintense (E). Hematoxylin and eosin (H&E) staining showed moderately-differentiated HCC; original magnification x 200 (F).

Figure 4

Hypervascular hepatocellular carcinoma (HCC) without washout in 44-year old man with non alcoholic fatty liver disease. Axial T2-weighted fat-suppressed image shows moderately hyperintense lesion (arrow) in segment VI (A). Dual-echo images show that tumor (arrows) is isointense on in-phase image (B) without signal drop on opposed-phase image, while background liver parenchyma shows diffuse signal drop as a consequence of fatty liver disease (C). The lesion (arrows) is hyperintense on diffusion-weighted image (D), hypevascular on arterial phase (E) without washout on portalvenous phase (F). On hepatobiliary phase the tumor (arrow) is hypointense (G). Hematoxylin and eosin (H&E) staining showed moderately-differentiated HCC with very dilatated sinusoidal network; original magnification x 200 (H).

Figure 5

Hepatocellular carcinoma (HCC) in 73-year old man with alcoholic cirrhosis. Axial T2-weighted fat-suppressed image shows slightly hyperintense well-defined nodular lesion (arrow) in segment VII (A). The lesion (arrows) is hypervascular on arterial phase (B) without washout on portal-venous phase (C). On hepatobiliary phase the tumor (arrow) is strongly hyperintense (D) with hyperintensity on diffusion-weighted image (E). Hematoxylin and eosin (H&E) staining showed well-differentiated HCC; original magnification x 200 (F).