Imaging Manifestations Of Small-diameter Mass-forming Intrahepatic Cholangiocarcinomas

Objectives:Ultrasound,computed tomography(CT)and magnetic resonance imaging(MRI)are commonly used to evaluate solid intrahepatic tumor lesions and to guide the preoperative evaluation and treatment establishment in clinic.Compared with hepatocellular carcinoma(HCC)and classic intrahepatic cholangiocarcinomas(ICCs),the imaging characteristics of small-diameter mass-like ICCs(diameter ?3 cm)are still unclear.Here we compared small-diameter mass-like ICCs with large-diameter mass-like ICCs and small HCCs,aiming to characterize the imaging manifestations of these small lesions.MethodsFirst a complete set of feasible inclusion criteria was established.Then the patients with small-diameter mass-like ICCs,large-diameter mass-like ICCs,and small HCCs were named as the small ICC group,the large ICC group,and the small HCC group,respectively.All patients were confirmed by pathological diagnosis.First,the clinical data of the three groups were summarized,and the small ICCs were compared with large ICCs and small HCCs separately.To characterize the ultrasound,CT and MRI images of small ICCs,we retrospectively analyzed the imaging data of all three groups,including ultrasonic examination,CT,MRI plain scans,enhanced scans,and diffusion-weighted imaging sequences.Both enhanced CT and enhanced MRI were three-phase dynamic enhancement,including arterial phase,portal phase,and delayed phase.First,the routine ultrasonic characteristics of the three groups were summarized,and the small ICCs were compared with large ICCs and small HCCs separately.Then the non-enhanced CT and MRI,and the enhanced CT and MRI images were summarized for all three groups,and the small ICCs were compared again with both large ICCs and small HCCs.Finally,the enhanced MRI images of small ICCs were compared among different diameters.Results:Totally 55 cases of small ICCs,75 cases of large ICCs,and 115 cases(all single nodules)of small HCCs were included.The small ICC group included 37 males and 18 females(mean age = 58 years old),accompanied with(12/55,21.8%)or without(43/55,78.2%)symptoms.The clinical manifestations of small ICCs are significantly different from those of large ICCs,but are not significantly different from the small HCCs.The small ICC group versus the small HCC group is found with a significantly lower rate of hepatitis B virus infection(60.0%vs.86.1%)and a significantly lower rate of liver cirrhosis(16.4%vs.64.3%).The rate of accompanied cholelithiasis is significantly higher in the small ICC group versus the small HCC group(21.8%vs.7.8%).The elevated rate of alpha fetoprotein(AFP)level is significantly lower in the small ICC group versus the small HCC group(1.8%vs.67.0%).The elevated rates of carcinoembryonic antigen and carbohydrate antigen 199 in the small ICC group versus the large ICC group are both significantly lower(10.9%vs.34.7%;27.3%vs.52.0%).Totally 49 small ICC patients received ultrasonic examinations and were manifested as homogeneous hypoechoic nodules,while the large ICCs were found with heterogeneous echoes(22.4%vs.94.4%).The lesions are round-like or irregularly shaped,while the small HCCs are mostly round-like(59.2%vs.79.6%).The rate of halo sign is significantly higher in the small ICC group versus the small HCC group(4.1%vs.38.8%).The rate of biliary dilation is significantly lower in the small ICC group versus the large ICC group,but not found in the small HCC patients(4.1%vs.0.0%).The seven patients undergoing ultrasonic angiography were manifested as wash in and wash out enhancement(6 cases)and fast in and slow out enhancement(1 case).Totally 29 small ICC patients received CT and were manifested as homogeneous round-like nodules,while the large ICC patients were found with heterogeneous irregular nodules(75.9%vs.38.6%;79.3%vs.56.1%).Calcification is rare among small ICC patients,but is not found among the small HCC patients.The rate of pseudocapsules is significantly lower in the small ICC group versus the small HCC group(0.0%vs.41.8%).The rate of peripheral biliary dilation is significantly higher in the small ICC group versus the small HCC group(20.7%vs.0.0%).The rate of lymph node enlargement is significantly lower in the small ICC group versus the large ICC group(6.9%vs.40.4%).At the arterial phase on enhanced CT,the rate of overall enhancement is significantly higher in the small ICC group versus the large ICC group(13.8%vs.1.8%),but is significantly lower versus the small HCC group(13.8%vs.75.4%).The rate of peripheral enhancement is significantly lower in the small ICC group versus the large ICC group(37.9%vs.68.4%),but is significantly higher versus the small HCC group(37.9%vs.3.1%).The rate of low enhancement is significantly higher in the small ICC group versus the large ICC group(37.9%vs.5.3%)and the small HCC group(37.9%vs.6.2%).At the portal phase,the small ICC group versus the small HCC group is found with a significantly higher rate of peripheral enhancement(27.6%vs.0.0%),but a significantly lower rate of low enhancement(55.2%vs.86.2%).At the delayed phase,the small ICC group versus the small HCC group is found with a significantly higher rate of partial enhancement(24.1%vs.3.1%),but a significantly lower rate of low enhancement(58.6%vs.89.2%).The ways of CT enhancement in the small ICC group are mainly peripheral plus progressive,and are significantly different from the small HCC group,but not from the large ICC group.The rates of persistent high enhancement and persistent low enhancement in the small ICC group are both significantly higher than the large ICC group(10.3%vs.0.0%;20.7%vs.5.3%),while the rate of peripheral enhancement is significantly lower(6.9%vs.31.6%).The rate of progressive enhancement in the small ICC group is significantly higher than the small HCC group(10.3%vs.1.8%),but the rate of washout enhancement is significantly lower(10.3%vs.58.5%).The 51 cases of small ICCs receiving MRI were manifested as round-like lesions with T1WI hypointensity and T2WI hyperintensity.The rate of homogeneous T2W sequence is significantly higher in the small ICC group versus the large ICC group(37.3%vs.0.0%),but is significantly lower versus the small HCC group(37.3%vs.73.2%).The small ICCs are found with clear margins and no necrosis,which are significantly different from the large ICCs(82.4%vs.24.6%;7.8%vs.31.9%).The rate of target signs in the small ICC group is insignificantly lower than the large ICC group,but is significantly higher versus the small HCC group(37.7%vs.8.5%).Like the enhanced CT,the enhanced MRI shows that pseudocapsules are nearly all found among the small HCC patients,while the accompanied rate of peripheral biliary dilation in the small ICC group is higher than the small HCC group.The rates of lymph node enlargement,satellite lesions,portal vein tumor emboli and adjacent organ invasion in the small ICC group are all higher than the large ICC group,but are not significantly different from the small HCC group.At the arterial phase on enhanced MRI,the rate of overall enhancement is significantly higher in the small ICC group versus the large ICC group(23.5%vs.1.4%),but is significantly lower versus the small HCC group(23.5%vs.80.5%).At the arterial phase and portal phase,the rates of peripheral enhancement in the small ICC group are significantly lower than the large ICC group,but are significantly higher than the small HCC group.At the portal phase,the rate of overall enhancement in the small ICC group is significantly lower than the large ICC group(21.6%vs.2.9%),but are not significantly different from the small HCC group.The rate of low enhancement in the small ICC group is significantly higher than the large ICC group(27.5%vs.4.3%),but is significantly lower versus the small HCC group(27.5%vs.61.0%).At the delayed phase,the rate of overall enhancement in the small ICC group is significantly higher than the other two groups.The rate of partial enhancement in the small ICC group is significantly lower than the large ICC group(23.5%vs.69.6%),but is significantly higher than the small HCC group(23.5%vs.3.7%).The rate of low enhancement in the small ICC group is significantly higher than the large ICC group(25.5%vs.4.3%),but is significantly lower versus the small HCC group(25.5%vs.81.7%).The rate of peripheral enhancement in the small ICC group is significantly lower than the large ICC group(39.2%vs.71.0%),and significantly higher than the small HCC group(39.2%vs.2.4%).The rates of peripheral enhancement and progressive enhancement in the small ICC group are both higher than the small HCC group.The rate of persistent high enhancement in the small ICC group is significantly higher than the large ICC group(17.6%vs.1.4%),without any fading,but is not significantly different from the small HCC group(0.0%vs.14.6%).The rate of washout enhancement in the small ICC group is significantly higher than the large ICC group(11.8%vs.0.0%),but is significantly lower versus the small HCC group(11.8%vs.76.8%).The patients with diameter? 2cm ICCs are mainly manifested on the enhanced MRI as progressive enhancement,and the rate of peripheral plus progressive enhancement is significantly lower than the ICCs in diameter 2-3 cm or>3 cm(5.6%vs.57.6%;5.6%vs.71.0%).The ICCs with smaller diameter were found with larger proportions of persistent high enhancement or washout enhancement.Conclusions:The small ICCs are usually asymptomatic in clinic and probably accompanied with hepatitis B virus infection,but rarely with liver cirrhosis.Laboratory tests show that the elevated rates of carcinoembryonic antigen and carbohydrate antigen 199 in the small ICC group are both significantly lower than the large ICC group.Ultrasonic examinations show that the small ICCs are mainly manifested as homogeneous hypoecho with clear or blur margins.The non-enhanced CT and MRI show that the tumors are usually round-like nodules with no capsules,rarely accompanied with calcification or necrosis.The small ICCs may be accompanied with hepatic capsule retraction and peripheral biliary dilation,which help with the discrimination from small HCCs,but are rarely accompanied with lymph node enlargement.The small ICCs are usually found with no satellite lesions,portal vein tumor emboli,or adjacent organ invasion.The enhanced CT and MRI show that the small-diameter ICCs are mostly manifested as peripheral plus progressive enhancement,which help with the discrimination from small HCCs.However,when the diameters of small ICCs are smaller,the enhancement of lesions on MRI varies largely in different ways.The enhanced MRI shows that the enhanced ways of smaller nodules are mostly progressive,and partly persistent high enhancement and washout enhancement.