Enhancement patterns of intrahepatic mass-forming cholangiocarcinoma at multiphasic computed tomography and magnetic resonance imaging and correlation with clinicopathologic features.

OBJECTIVE: Incidence of intrahepatic mass-forming cholangiocarcinoma (IMCC) is increasing worldwide, especially in patients with chronic liver disease. The small and the histologically well-differentiated IMCCs in chronic liver disease could be arterially hypervascular lesions with/without washout on computed tomography (CT) and magnetic resonance imaging (MRI), mimicking typical hepatocellular carcinoma (HCC). The aim of this work is to evaluate contrast enhancement (CE) patterns of IMCCs at quadri-phasic multidetector CT (4-MDCT) and MRI, using imaging-clinicopathologic correlation. PATIENTS AND METHODS: The 4-MDCT and MR images of 56 histologically confirmed IMCCs were retrospectively evaluated for tumor morphology and enhancement features. Enhancement pattern was defined according to the behavior of the nodule in arterial (AP), portal venous (PVP) and equilibrium phases (EP), and dynamic pattern was described according to enhancement progression throughout the different phases. Arterial and dynamic enhancement patterns were correlated with chronic liver disease, tumor size and histological differentiation. RESULTS: Most of the nodules were peripherally hyperenhancing (50%) on AP, and partially hyperenhancing on PVP (67.9%) and EP (80.3%). Forty-six (82.1%) IMCCs showed progressive CE, 7 (12.5%) stable CE and 3 (5.4%) wash-out. In normal liver there were 34 nodules with progressive and 3 with stable CE, whereas in chronic liver disease there were 12 IMCCs with progressive, 4 with stable and 3 with washout pattern (p = 0.01); IMCCs with progressive CE were more differentiated than IMCCs with stable CE and wash-out (p = 0.02). CONCLUSIONS: The most prevalent enhancement pattern of IMCCs was arterial rim enhancement followed by progressive and concentric filling. The stable and the washout patterns were more frequent in poorly differentiated IMCCs. Contrast washout was observed only in IMCCs emerging in chronic liver disease with a risk of misdiagnosis with HCC.