Intrahepatic cholangiocellular carcinoma with radiological enhancement patterns mimicking hepatocellular carcinoma.

Non-invasive diagnosis of hepatocellular carcinoma (HCC) in cirrhotic patients requires demonstration of wash-in and wash-out on contrast-enhanced imaging. Recent studies have reported misclassification of mass-forming intrahepatic cholangiocarcinoma (MFCCC) as HCC. We aimed to analyze the contrast enhancement patterns of MFCCC, focusing especially on lesions mimicking HCC. We retrospectively evaluated all consecutive patients with MFCCC who underwent surgery between 2007 and 2017. Patients with mixed HCC-MFCCC were excluded. Two expert radiologists reviewed preoperative CT and MRI. Full-nodule hyperenhancement in the arterial phase in conjunction with hypoenhancement in the portal/late phase was classified as an "HCC-like pattern". Imaging of MFCCCs with an HCC-like pattern was reviewed by an additional radiologist blinded to clinical data. Ninety-two patients were analyzed. All patients were investigated with multiphase CT and 85 with MRI. Twelve tumors (13%) showed full-nodule arterial hyperenhancement. Of these, four were hypoenhancing in the portal/late phase. Overall, 4/92 (4%) MFCCCs (4/45 in patients with cirrhosis/hepatitis, 9%) showed an HCC-like pattern accounting for misclassification as HCC on imaging review. HCC-like MFCCCs accounted for 9% of single tumors ≤ 50 mm. All HCC-like MFCCCs occurred in patients with cirrhosis or hepatitis, whereas only 47% of non-HCC-like MFCCCs did so (p = 0.053). After a median follow-up of 29 months, all patients with HCC-like MFCCCs are alive and disease free (median 64 months). In conclusion, MFCCC was misdiagnosed as typical HCC in 4% of all cases and in 9% of patients with single tumors ≤ 50 mm or with cirrhosis/hepatitis. The risk of misdiagnosis should be considered prior to treatment planning.