Imaging features of intrahepatic biliary cystadenoma(cystadenocarcinoma) on ultrasound and contrast-enhanced ultrasound

Objective To evaluate the imaging features of intrahepatic biliary cystadenoma(cystadenocarcinoma)on baseline and contrast-enhanced ultrasound(CEUS),and differentiate malignant from benign tumor.Methods The imaging features of 5 intrahepatic biliary cystadenoma cases and 5 intrahepatic biliary cystadenocarcinoma cases were retrospectively analyzed,the diagnosis was proven by pathology after surgical resectionin.All of the lesions were solitary.Results All of the 5 cystadenoma cases were cystic or with an intracystic solid component less than 50%;however,only 1 of the 5 cystadenocarcinoma cases was cystic or intracystic,solid component was less than 50%.All of the 5 cystadenoma cases were multiloculated;only 1 of the 5 cystadenocarcinoma cases was multiloculated.Solid component over 50% or cystic lesions with solid nodules more than 1.0 cm in diameter on the wall were observed in 4 out of 5 cystadenocarcinoma cases.Correspondingly,only 1 out of 5 cystadenoma cases showed mural nodule,but less than 1.0 cm in diameter.On baseline ultrasound,biliary cystadenomas were more likely to be shown as multilocular,cystic lesion or with an intracystic solid component less than 50%,cystadenocarcinomas were more likely to present the features of solid component greater than 50% or mural nodule with a diameter over 1.0 cm.(Fisher exact test,all P=0.048).On contrast-enhanced ultrasound,hyper-(n=3)or iso-enhancement(n=2)was presented in the cystic wall,septum or mural nodules of the cystadenomas during the arterial phase,the enhancement washed out to be hypo-enhancement in all the lesions during the late phase.Cystadenocarcinomas also showed hyper-(n=3)or iso-enhancement(n=2)in the cystic wall,septum and mural nodules during the arterial phase and hypo-enhancement during the late phase.There was no significant difference between cystadenoma and cystadenocarcinoma in the enhancement pattern of arterial and late phases(Fisher exact test,both P=1.00).Four in 5 cystadenoma cases were correctly diagnosed on CEUS,but none in cystadenocarcinoma cases.Conclusions Intrahepatic biliary cystadenoma(cystadenocarcinoma)has characteristic features on baseline ultrasound.CEUS,as a solid supplement of baseline ultrasound,is helpful in evaluating the cystic wall,septation,solid component and nodule vascularity.