A case of cystic intraductal papillary neoplasm of the bile duct with associated adenocarcinoma.

The pathophysiology of intraductal papillary neoplasm of the bile duct (IPNB) remains unclear. We report a case of a Japanese man in his 70s with this disease, which we first diagnosed as a liver cyst. The patient was followed at our hospital for a 10-mm liver cyst and a 10-mm pancreatic cyst for 4 years. Four years later, tumor markers including CA19-9 were elevated in his blood tests. Abdominal ultrasonography showed a heterogeneous hyper-echoic mass with an anechoic area, 25 × 25 mm, in the S2 liver segment and showed posterior echo enhancement. Contrast-enhanced computed tomography showed that the tumor was gradually enhanced slightly. Magnetic resonance imaging showed a lesion of T1 low, T2 high around the cyst. Endoscopic retrograde cholangiopancreatography did not show an abnormality, including findings of the duodenal papilla. We suspected an IPNB and performed left lobe hepatectomy. The resected whitish tumor around the cyst was 25 × 23 mm. The tumor contained an intraductal papillary mass with an adjacent invasive adenocarcinoma. The papillary mass with fine vascular cores was lined by foveolar-type epithelium. Our diagnosis was IPNB with invasive adenocarcinoma. This case indicates that IPNB should be considered in the differential diagnosis of liver cysts.