Small hepatocellular carcinoma with bile duct tumor thrombi: CT and MRI findings

Small hepatocellular carcinoma (sHCC) with bile duct tumor thrombi (BDTT) is rare and easily misdiagnosed as cholangiocarcinoma. This study was to analyze the imaging features of sHCC with BDTT. CT and/or MRI examinations were performed on seven patients who had sHCC with BDTT. One patient received CT scan, one received CT and MR scan, and five received MR scan. Magnetic resonance cholangiopancreatography (MRCP) was performed in five patients. The diagnosis of sHCC with BDTT was based on surgical specimens in all patients. The sHCC lesions and BDTT were presented on CT or MRI scans in all the seven cases. The BDTT is presented as soft tissue mass in the bile duct with biliary dilatation above the obstruction. In the two patients who had received dynamic contrast CT scan, the sHCC lesions showed atypical enhancement pattern of HCC. The BDTT showed similar enhancement pattern as sHCC in one of the two patients. The sHCC and BDTT showed homogenous hypointense signals on T1W images and hyperintense signals on T2W images in all six cases. In the three patients who had received dynamic enhancement MR scan, the enhancement patterns of sHCC lesions and BDTT were similar. Early enhancement of sHCC lesion and BDTT at hepatic arterial phase with hyperintense signals was observed in one patient, while two other patients had no early enhancement. All sHCC lesions and BDTT showed hypointense signals at portal venous phase, equilibrium phase, and delayed phase. Six patients showed hyperintense signal of hemorrhage in the dilated bile ducts on both T1W and T2W images. Five cases of BDTT presented as filling defect in the bile ducts on MRCP. The BDTT were directly connected with sHCC lesions in all the seven patients, without bile duct wall thickening or extra-bile duct invasion. CT or MRI is a safe, reliable, and valuable method for the detection and diagnosis of sHCC with BDTT.