1428 Biliary Obstruction Due to Extrahepatic Biliary Mucinous Cystic Neoplasm: An Uncommon Case

Abstract

INTRODUCTION: Biliary mucinous cystic neoplasms (BMCNs) are a rare form of premalignant biliary cystic tumors, much like their better-known counterpart, biliary intraductal papillary mucinous neoplasms (IPMNs). BMCNs most commonly occur in females during the 5th decade of life. They account for approximately 1-5% of all liver cysts. The lack of awareness of these lesions poses a challenge for proper and timely diagnosis. Here, we present an interesting case of extrahepatic BMCN. CASE DESCRIPTION/METHODS: A 30-year-old female presented with pruritis, dark urine, and light-colored stools. Labs revealed transaminitis and elevated bilirubin concerning for biliary obstruction. Abdominal ultrasound showed cholelithiasis and dilation of the distal common bile duct (CBD) concerning for choledocholithiasis. MRCP was performed and described a 2.2 × 2.4 cm cystic dilatation of the extrahepatic bile duct involving the distal common hepatic duct (CHD) concerning for either type 1B or type II choledochal cyst. Endoscopic ultrasound revealed a CHD cystic lesion with internal debris concerning for either sludge or biliary IPMN (Figure 1). ERCP with cholangioscopy revealed papillary projection in the CHD (Figure 2). Directed biopsies revealed mucinous epithelium with cytologic atypia. The patient was referred for complete resection of the CBD and CHD, cholecystectomy, and Roux-en-Y hepaticojejunostomy. Surgical pathology revealed a tumor consisting of a cystic structure lined by mucinous epithelium with estrogen receptor (ER) positive ovarian-type stroma, and mild to focal moderate dysplasia, consistent with noninvasive extrahepatic BMCN (Figure 3). DISCUSSION: BMCNs are often detected incidentally when investigating other common causes of biliary disease. The overall incidence of BMCNs is approximately 1:20,000 to 1:100,000. They are most commonly found within the liver (90%), are rarely extra-hepatic, and they seldom present with obstructive jaundice. The treatment of choice is surgical resection. Diagnosis is made via histological confirmation of ovarian-type stroma. The location of the lesion, in this case, is more common for IPMNs. Both IPMNs and BMCNs carry malignant potential requiring complete resection for diagnosis and treatment. With the risk of malignant transformation as high as 30%, an awareness of these rare neoplasms is very important.