Abstract
A cystic nodule, 15 mm in diameter, was detected by ultrasonography (US) in the S4 segment of the left hepatic lobe in a 78-year-old male who achieved eradication of hepatitis C virus and was undergoing regular US surveillance every 6 months. A solid nodule, 8 mm in diameter, was found in this cystic nodule 20 months after detection of the cystic nodule and was subjected to further evaluation. A solid part was enhanced in the arterial phase of contrast-enhanced US (CEUS), whereas the imaging evaluation of this solid nodule was difficult by computed tomography or magnetic resonance cholangiopancreatography due to its minute size. The B4 bile duct was not depicted by endoscopic retrograde cholangiography (ERC), but intraductal US (IDUS) from the B2＋3 bile duct depicted a hyperechoic nodule at the proximal site of the B4 branch. CEUS and ERC findings of this nodule suggested intraductal papillary neoplasm of the bile duct (IPNB), and the left hepatic lobe and the caudate lobe were resected surgically. Macroscopic examination of the resected specimen revealed a multilocular lesion including a papillary nodule, and the pathologic diagnosis was papillary adenocarcinoma without interstitial infiltration. The morphology of tumor cells was similar to that of gastric epithelium, and therefore we diagnosed this nodule as gastric IPNB. This case showed that US surveillance was useful for the detection of cystic and solid nodules in an early stage. Moreover, CEUS provided useful findings for an accurate diagnosis of IPNB.
