Differentiating Features of Atypical Hepatocellular Carcinoma vs Intrahepatic Mass-Forming Cholangiocarcinoma in Contrast-Enhanced MRI

Hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma share common clinical manifestations and risk factors, making differential diagnosis challenging in some cases. A study published in Frontiers in Oncology identified several reliable contrast-enhanced magnetic resonance imaging (MRI) features to help differentiate atypical HCCs with peripheral rim-like enhancement from intrahepatic mass-forming cholangiocarcinoma (IMCC).

MRI is commonly used to preoperatively diagnose and evaluate liver tumors. The characteristic vascular profile of HCC is typically identified by hyperenhancement in arterial phase and washout on portal or delayed phase images. However, approximately 40% of HCCs have atypical imaging features, including arterial phase hypovascularity or peripheral rim-like enhancement.

“Currently, these HCCs with atypical imaging features pose a significant diagnostic challenge to radiologists,” the study authors wrote. “In particular, HCC is difficult to differentiate from IMCC if it presents with peripheral rim-like enhancement in the arterial phase followed by gradual filling of the contrast media.”

HCCs and IMCCs have significantly different prognostic considerations and treatment options, so distinguishing between them is crucial. The study aimed to provide reliable imaging features to assist in differentiation between IMCCs and atypical HCCs with peripheral rim-like enhancement on contrast-enhanced MRI.

A total of 168 patients with confirmed HCCs or IMCCs were included in the study. Of the overall cohort, 85 patients had HCC and 83 had IMCC.

Inclusion criteria were a complete histopathologic description of HCCs or IMCCs; a dynamic contrast-enhanced liver MRI within 1 month before operation; HCCs showing atypical imaging features of peripheral rim-like enhancement in dynamic contrast-enhanced liver MRI; and no tumor treatment prior to the preoperative MRI. Two radiologists blinded to the histopathological findings independently evaluated the imaging features, and the case was included in the study when results of their assessments were consistent.

HCCs more commonly featured a round contour, smooth margin, and heterogeneous SI on T1WI or T2WI, whereas IMCCs more commonly featured a lobulated contour, non-smooth margin, and homogeneous SI on T1WI or T2WI. A thick rim on atrial phase images was more common in HCCs, as was diffusely low SI on DP images. IMCCs showed a thin rim on atrial phase images and target sign on DP images more frequently.

Significant imaging features of IMCCs also included bile duct dilation, surface retraction, target sign on diffusion-weighted imaging, and lymph node enlargement. In HCCs, radiological capsule, intralesional fat, central brightness on T2WI, and portal vein embolus were notable imaging features.

Overall, the study identified radiological capsule, heterogeneous signal intensity (SI) on T1-weighted turbo field-echo in-phase and opposed sequence (T1WI), a lobulated contour, target sign on delay phase (DP), and bile duct dilatation as differentiating features in HCCs versus IMCCs.

Researchers also created a diagnostic model using the 5 independent differential factors. The model achieved a sensitivity of .88 and specificity of .906, demonstrating excellent accuracy in distinguishing atypical HCCs with peripheral rim-like enhancement from IMCCs.

The study was limited by its retrospective nature and its single-center population, as well as its small size. The model is also not easy to implement in daily clinical practice, although the authors aim to apply the results into clinical practice going forward. Further research into laboratory indicators of atypical HCCs versus IMCCs would also be helpful.

“Our findings may help radiologists better to differentiate HCCs with atypical enhancement patterns from IMCCs, thereby providing clinicians with more accurate preoperative imaging diagnoses to select appropriate treatment options,” the study authors concluded.

Reference

Zhang S, Huo L, Feng Y, et al. Preoperative differentiation of hepatocellular carcinoma with peripheral rim-like enhancement from intrahepatic mass-forming cholangiocarcinoma on contrast-enhanced MRI. Front Oncol. Published online November 23, 2022. doi:10.3389/fonc.2022.986713