2.3 Outcome and Follow-up
The patient had good postoperative recovery after postoperative intensive care management for COPD exacerbation. The histopathological evaluation of the resected specimen revealed variable-sized cysts lined with columnar cells having basal nucleus and apical mucin. The cyst contained mucinous material. The surrounding liver tissue showed fibrosis encircling hepatocytes forming parenchymal nodules but lacked ovarian-like stroma. (Figure 2) The patient is doing well in the follow-up of 1 year with no recurrence.
3 Discussion
The cyst leading to atrophy of the left lobe of the liver, radiological communication of dilated intrahepatic bile ducts within, and absence of ovarian-like stroma makes our case unique. World Health Organisation (WHO) in 2010 proposed uniform terminology of mucinous cystic neoplasm in the presence of ovarian-like stroma (OS) or intraductal papillary mucinous neoplasm of bile duct (IPMN-B) in the presence of biliary tree communication.2 However, the presence of OS and demonstration of bile duct communication is not present in all cases.3 The literature does not clarify whether cystadenoma without OS is a discrete entity or IPMN-B where biliary communication could not be established. The prevalence of these cysts compared to those with OS is lower4 but few studies have shown equal prevalence as well.5 Most IPMN-B cases have been described as tubular or fusiform dilatation of bile ducts similar to IPMN of the pancreas.6 The rate of malignancy in IPMN-B (60% - 70%) is higher than that of the pancreatic counterpart of IPMN (23%-30%).7,8 The presence of mural nodules suggesting malignancy is commonly present except in benign cases.7 The stage of malignancy in IPMN-B is however less advanced.1
Cystic IPMN-B is an uncommon variant as in the index case resembling branch duct IPMN of the pancreas.6 These cysts have been thought to arise from prebiliary glands located within the wall or scattered in the surrounding connective tissue of the larger bile duct.9 It has equal sex predilection and peaks in the sixth decade.1,10 The cystic IPMN-B is frequently associated with mural nodules and bile duct dilatation distal to the cyst.7 This is attributed to mucus from cysts in the bile duct leading to obstruction and dilatation, which in the long run could lead to liver atrophy as in the index case. Mucobilia may result in transient biliary obstruction or recurrent cholangitis.1 The risk factors are shown to be hepatolithiasis, Clonorchis infections, etc.11Although biliary communication is a key feature, CECT or magnetic resonance imaging cannot always demonstrate luminal communication, probably due to narrow communications.12 However, the biliary communication in the background of the atrophic liver was well demonstrated by a CT scan in the index case. Cyst fluid CEA in the index case was normal. The exact correlation of CEA to cystic IPMN-B is scarcely described in literature, but higher fluid CEA has been associated with cystadenocarcinoma.13
All Cystic IPMN-B requires resections, preferably with intraoperative cholangiogram to demonstrate biliary communication and to rule out mucus plugs in the bile duct. Preoperative endoscopic retrograde cholangiography or intraoperative cholangiography (IOC) is more reliable as macroscopic examination is often accurate.14 IOC was not used in the index case due to logistic issues. Although the index case had no malignant foci, most of the cases have malignant foci which warrant formal hepatectomy in all cases. Additionally, extrahepatic bile duct resection and lymph node sampling may also be required in case of malignant cysts. The prognosis after resection is good compared to intrahepatic or hilar cholangiocarcinoma with 5-year survival of 60% to 80%.10 The columnar cells and MUC1 expression adversely impact survival.1,10