Intracholecystic Papillary Neoplasm Localized to the Cystic Duct: A Case Report.

Intracholecystic papillary neoplasm (ICPN) of the gallbladder is a premalignant lesion. An ICPN arising from the cystic duct is rare. A woman in her 60s exhibited dilatation of the common bile duct on computed tomography (CT) performed for screening of respiratory disease. The CT revealed an enhancing mass, 3.3 cm in diameter, in the cystic duct. Endoscopic ultrasonography showed a well-demarcated, hyperechoic mass in the dilated cystic duct. Endoscopic retrograde cholangiography showed that the common bile duct was slightly retracted by the dilated cystic duct. Cytological analysis of the bile juice did not show any evidence of malignancy. She was diagnosed with a cystic bile duct tumor suggestive of ICPN. Cholecystectomy, resection of the extrahepatic bile duct, and lymph node dissection were performed. Macroscopically, the papillary-proliferated tumor was localized to the cystic duct. No critical lesions were evident in the common bile duct. Histologically, the tumor in the cystic duct showed intraluminal growth with a papillary configuration without malignancy. Based on these findings, the tumor was diagnosed as an ICPN. We encountered a rare case of ICPN localized to the cystic duct of the gallbladder.