Intrahepatic Mass-forming Cholangiocarcinomas: Enhancement Patterns at Multiphasic CT, with Special Emphasis on Arterial Enhancement Pattern-Correlation with Clinicopathologic Findings

Purpose: To evaluate the imaging features of intrahepatic mass-forming cholangiocarcinomas (IMCCs) at computed tomography (CT), with a special emphasis on the degree and pattern of arterial enhancement, and to determine whether the clinicopathologic features of IMCCs with arterial enhancement differ from those of IMCCs with less arterial enhancement. Materials and Methods: The institutional review board of Seoul National University Hospital approved this retrospective study, and informed patient consent was waived. Sixty-four patients with 70 pathologically confirmed IMCCs after surgical resection underwent multiphasic CT-unenhanced, hepatic arterial phase (HAP), portal venous phase, and/or equilibrium phase imaging. CT images were retrospectively evaluated for tumor morphology and enhancement features. Patients were placed into typical or atypical enhancement groups according to the presence of enhancement in the largest volume (>50%) of the tumors during the HAP. Imaging features of IMCCs were correlated with pathologic features. The typical and atypical enhancement groups were compared with respect to disease-free survival and overall survival. Survival rates were calculated by using the Kaplan-Meier method, and differences in survival were compared by using the log-rank test. A Cox proportional hazards model was used for multivariate survival analysis. Results: Fifty (71%) of 70 IMCCs showed typical arterial enhancement, and 20 (29%) showed atypical enhancement. The mean diameter of atypical IMCCs was significantly smaller than that of typical IMCCs (P = .001). Chronic liver disease was more frequent in the group with atypical lesions (P = .021). During the HAP, the prevalent enhancement pattern in this group was a mixed pattern of peripheral rim and internal heterogeneous enhancement. At pathologic evaluation, atypically enhancing IMCCs showed less central stroma and necrosis and larger cellular areas and more frequently had a cholangiolocellular component than typically enhancing IMCCs. Arterial enhancement of IMCCs was found to be an independent prognostic factor for longer disease-free survival. Conclusion: Arterially enhancing IMCCs were not rare; thus, enhancement pattern analysis of arterially enhancing IMCCs will be helpful in differentiating them from hepatocellular carcinomas. In addition, arterial enhancement of IMCCs appears to correlate with disease-free survival. (C) RSNA, 2011