Cholangiocarcinoma in cirrhosis: absence of contrast washout in delayed phases by magnetic resonance imaging avoids misdiagnosis of hepatocellular carcinoma.

This study assesses the magnetic resonance (MR) features of intrahepatic cholangiocarcinoma (ICC) in patients with cirrhosis with specific analysis of the contrast enhancement pattern. Cholangiocarcinoma may show increased contrast uptake in the arterial phase, and, if washout in the delayed venous phase were to be detected, the noninvasive diagnostic criteria proposed in the American Association for the Study of Liver Diseases guidelines would be refuted. We reviewed the MR findings of 25 patients with cirrhosis with 31 histologically confirmed ICC nodules. Signal intensity on basal T1-weighted and T2-weighted images and characteristics of enhancement after contrast administration on arterial, portal, and delayed phase were registered. Enhancement pattern was defined according to the behavior of the lesions in each phase, and dynamic pattern was described according to the progression of enhancement throughout the different phases. The most frequent pattern displayed by ICC was a progressive contrast uptake (80.6%). Stable contrast enhancement was registered in 19.4%. None of the ICCs showed a washout pattern, a profile that is specific for hepatocellular carcinoma (HCC). The ICC dynamic behavior differed significantly according to tumor size: progressive enhancement pattern was the most frequent (20 of 25 cases) in lesions larger than 20 mm, whereas the stable pattern was mainly identified in nodules smaller than 20 mm. The most characteristic MR contrast pattern in ICC in cirrhosis is a progressive contrast uptake throughout the different phases, whereas contrast washout at delayed phases is not observed. Because stable enhancement pattern without washout also can be registered in small HCC nodules, the evaluation of delayed phase is mandatory for a proper nodule characterization. If washout is not registered, a biopsy should be mandatory for diagnosis.