Biliary IPMN

Published on 19/07/2015 by admin

Filed under Radiology

Last modified 22/04/2025

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 Massively dilated bile ducts (either diffuse or localized) filled with mucin

image Mural nodules best visualized after removal of mucin
image Biliary dilation both proximal and distal to mural nodule
• CT/MR: Markedly dilated intra-/extrahepatic bile ducts with mural nodularity or discrete intraductal mass

image Attenuation and MR signal characteristics of mucin distending ducts is similar to normal bile
image Presence of mural nodularity or soft tissue suggests presence of malignancy

PATHOLOGY

• Unknown etiology, but associations with hepatolithiasis and Clonorchis suggest chronic biliary inflammation may be causative

CLINICAL ISSUES

• Most common in elderly patients from East Asia
• May present with repeated episodes of cholangitis and jaundice
• Biliary IPMN localized to intrahepatic ducts may be treated with partial hepatectomy if tumor is relatively localized
• Resection of the common duct with Roux-en-Y anastomosis may be required for tumors involving either extrahepatic duct or right/left main ducts
• Stenting or drainage to alleviate jaundice in patients who are not surgical candidates
• Multifocality frequent, and recurrences after surgery are common due to small foci of undetected disease in biliary tree distant from site of resection
image
(Left) Graphic of biliary intrapapillary mucinous tumor demonstrates the segmental distension of the right lobe intrahepatic ducts image, which are filled with mucin and contain a mucosal mass image arising from the ductal epithelium.

image
(Right) Axial T1WI MR with gadolinium in a woman with midepigastric pain and elevated alkaline phosphatase shows fusiform dilatation of the left bile ducts image, which proved to be biliary IPMN at surgery.
image
(Left) Axial CECT in a patient presenting with RUQ pain and elevated alkaline phosphatase demonstrates atrophy of the left lobe and marked dilation of the left bile duct image greater than the right. ERCP and subsequent surgery revealed a left duct biliary IPMN.

image
(Right) Axial CECT shows asymmetric left biliary ductal dilatation image and subtle enhancing nodularity within the proximal left duct image. Intraductal cholangiocarcinoma and background biliary IPMN were identified at histology. (Courtesy S. Yeon Kim, MD.)

TERMINOLOGY

Abbreviations

• Intraductal papillary mucinous neoplasm (IPMN) of bile ducts

Synonyms

• Intraductal papillary neoplasm of liver, mucin-secreting biliary papillomatosis, mucin-producing cholangiocarcinoma, mucinous ductal ectasia of biliary tree

Definitions

• Mucin-producing papillary neoplasm arising from biliary mucosa

image Only recently added to WHO classification in 2010
image Significant overlap with biliary papillomatosis, and some authors suggest they are same entity

IMAGING

General Features

• Best diagnostic clue

image Diffuse segmental “aneurysmal” dilation of bile ducts with a polypoid or nodular intraductal mass
image Biliary dilation both proximal and distal to mural nodule due to mucin hypersecretion
• Location

image Intra-/extrahepatic bile ducts: Most common locations are left liver lobe ducts and liver hilum
• Size

image  
• Morphology

image “Aneurysmal,” marked dilatation of mucin-distended ducts

Radiographic Findings

• ERCP

image Extrusion of clear mucin from patulous ampulla visible to endoscopist due to mucin hypersecretion by tumor
image Massively dilated bile ducts (either diffuse or localized) filled with mucin

– Mucin-filled bile ducts may result in nonvisualization of affected segment(s) due to difficulty of filling mucin-filled ducts with contrast
– Amorphous filling defects in dilated ducts may representing either mucin plugs or tumor
image Mural nodules best visualized after removal of mucin

CT Findings

• Markedly dilated intra-/extrahepatic bile ducts with mural nodularity or discrete intraluminal papillary/fungating mass

image Attenuation of mucin distending ducts is similar to normal bile

– Mucin within ducts cannot be differentiated from normal bile on CT
image Presence of mural nodularity or soft tissue component should suggest presence of malignancy
• CT cholangiography may play a role in preoperative diagnosis and determination of tumor resectability: Mucin (and tumor) outlined by biliary contrast

MR Findings

• Diffuse or segmental biliary ductal dilatation with bile duct contents appearing hyperintense on T2WI and hypointense on T1WI (similar to normal bile)

image Mucin within ducts cannot be differentiated from normal bile on MR
image ERCP/MRCP mismatch: Mucin-filled duct is not visible on ERCP while it is seen on MRCP
image Hepatobiliary contrast agents (i.e., Eovist) may demonstrate nonfilling of affected ducts (i.e., those filled with mucin), similar to ERCP
• Papillary projections or discrete soft tissue masses within dilated ducts appear hypointense on T1WI, hyperintense on T2WI, and enhancing on T1WI C+

image Enhancing mural nodularity raises concern for malignancy

Ultrasonographic Findings

• Grayscale ultrasound

image Complex “mass” of aneurysmally dilated bile ducts
image Echogenic intraductal masses juxtaposed against anechoic mucin filling duct
image Linear echoes within dilated ducts may suggest mucobilia (layer sign)
image No flow in dilated bile ducts
• Endoscopic ultrasound (EUS) has reported higher sensitivity and accuracy

Nuclear Medicine Findings

• PET/CT

image Malignant biliary IPMN has increased FDG avidity

Imaging Recommendations

• Best imaging tool

image CECT, MRCP
• Protocol advice

image  

DIFFERENTIAL DIAGNOSIS

Biliary Cystadenoma/Cystadenocarcinoma

• Primary cystic liver mass (typically multilocular) with internal septations, mural nodularity, and calcifications
• No communication with bile ducts: Any mucin produced by tumor is confined to mass itself
• Most common in middle-aged women
• Typically has ovarian-type stroma

Cholangiocarcinoma

• Conventional cholangiocarcinoma manifests as infiltrative or nodular mass arising from biliary tree with biliary stricture, but without mucin production
• Malignant biliary IPMN is a rare form of peripheral cholangiocarcinoma (papillary form) characterized by intraductal growth

image Potential to spread along mucosal surfaces: Should prompt wide resection
image Constitutes 3-9% of cholangiocarcinomas with more favorable prognosis compared to more common mass-forming or periductal infiltrating cholangiocarcinoma
• Often will demonstrate delayed enhancement on multiphase imaging

Recurrent Pyogenic Cholangitis

• Disease characterized by cast-like pigment stones throughout biliary tree, biliary strictures resulting in intra- and extrahepatic biliary dilatation, and repeated bouts of cholangitis
• Most common in patients living in or from Southeast Asia
• Filling defects within biliary tree represent stones (not mucin or tumor as with biliary IPMN)

Pyogenic Liver Abscess

• Multiloculated cystic mass in liver with a thick, enhancing wall and surrounding liver parenchymal edema

image “Cluster” sign: Low-attenuation abscess locules
• No dilated bile ducts, mucin production, or intraductal mass
• Clinical history of fever and sepsis

Bacterial Cholangitis

• Typically secondary to biliary obstruction (most often due to choledocholithiasis)
• Bile duct walls appear thickened and hyperenhancing with heterogeneous liver parenchymal perfusion (particularly on arterial phase imaging)
• Infectious debris or pus within dilated bile ducts may mimic the presence of intraductal mucin or tumor

PATHOLOGY

General Features

• Etiology

image Unknown, but strong associations with hepatolithiasis and  Clonorchis, suggesting chronic biliary inflammation may be a causative factor
• Genetics

image No known genetic disposition
• Associated abnormalities

image Rupture with intraperitoneal mucinous mass: Pseudomyxoma
image Cases in East Asia strongly associated with biliary stones (especially hepatolithiasis) and  Clonorchis infection
• Extensive mucin formation in dilated ducts
• Nodular intraductal tumors

Staging, Grading, & Classification

• Types (based on morphology)

image Ductectatic type: Tumor in diffusely dilated bile duct
image Cystic type: Large cystic lesion communicating with bile duct
image Intermediate type: Cystic lesion communicating with bile duct + solid tumor
image Analogous to classification of pancreatic IPMN into main branch, side branch, and mixed subtypes
• Types (based on imaging appearance)

image Type I: Diffuse ductal dilatation with visible intraductal mass
image Type II: Diffuse ductal dilatation without visible intraductal mass
image Type III: Intraductal papillary mass with localized ductal dilatation
image Type IV: Mild ductal dilatation with intraductal cast-like lesions (either mucin plugs or tumor)
image Type V: Focal stricture-like lesion with mild proximal biliary dilatation

Gross Pathologic & Surgical Features

• Markedly distended, mucin-filled bile ducts with frond-like papilloma

Microscopic Features

• Counterpart of pancreatic IPMN

image Papillary tumor of bile duct mucosa
image Columnar epithelial cells arranged in innumerable papillary fronds distending bile ducts
image Often associated with mucin hypersecretion
image Strong tendency for multifocal disease (papillomatosis)
• Spectrum: Adenomatous dysplasia to frank invasive adenocarcinoma; usually coexist
• Premalignant lesion with high potential for malignancy: Adenoma to carcinoma sequence
• Likely a precursor to intraductal papillary cholangiocarcinoma

CLINICAL ISSUES

Presentation

• Most common signs/symptoms

image Most common presentation is repeated bouts of acute cholangitis: Abdominal pain, fever, chills, jaundice

– Biliary obstruction due to tumor, ↑ mucin production, or detached tumor fragments
– Intermittent biliary obstruction may mimic symptoms of biliary calculi or recurrent pyogenic cholangitis
image Some patients may be asymptomatic
• Other signs/symptoms

image ↑ CEA common: More likely to be ↑ in patients with malignant biliary IPMN or large mucin secretion
image Other laboratory markers may be elevated due to biliary obstruction: ↑ ALT/AST, bilirubin, GGT
• Clinical profile

image Asian patient with recurrent abdominal pain and fever

Demographics

• Age

image 5th through 7th decades
• Gender

image No clear gender predilection
• Ethnicity

image Most common in patients from East Asia

Natural History & Prognosis

• Repeated episodes of cholangitis and jaundice (due to biliary obstruction by the mass, tumor emboli, or mucin)
• Good prognosis for adenomas or dysplasia; invasive cancer prognosis depends on nodal status

image Invasive papillary cholangiocarcinoma has an overall better prognosis than more common mass-forming and periductal infiltrating cholangiocarcinoma subtypes
• High rates of recurrence (20% at 5 years for benign IPMNs and 60% at 5 years for malignant IPMNs)

image Multifocality frequent, and recurrences likely due to small foci of undetected disease in biliary tree distant from site of resection
image Close follow-up required due to high rates of recurrence

Treatment

• Biliary IPMN localized to intrahepatic ducts may be treated with partial hepatectomy if tumor is relatively localized
• Resection of the common duct with Roux-en-Y anastomosis may be required for tumors involved either extrahepatic duct or right/left main ducts
• Patients who are not surgical candidates due to extent of disease treated palliatively with stenting or drainage to alleviate jaundice

DIAGNOSTIC CHECKLIST

Consider

• Differentiate biliary IPMN from conventional cholangiocarcinoma

Image Interpretation Pearls

• Consider biliary IPMN in patients with aneurysmal dilation of biliary tree (often in a segmental or lobar distribution) with nodular enhancing intraductal tumor
image
(Left) ERCP in a patient with RUQ pain and elevated bilirubin demonstrates a grossly dilated common bile duct filled with amorphous mucin image, found to be a biliary IPMN.

image
(Right) Axial CECT shows a multiloculated cystic liver mass image with an irregular wall and contiguity with the biliary tree. Note the dilated common duct image, which communicates with the mass. This was found to be malignant degeneration of a biliary IPMN, with much of the “mass” representing dilated intrahepatic ducts filled with mucin.
image
(Left) ERCP of a patient with jaundice shows amorphous linear filling defect image within a dilated common duct. CECT (not shown) revealed marked asymmetric right and common bile duct dilatation. (Courtesy S. Yeon Kim, MD.)

image
(Right) Endoscopic image of the duodenum in the same patient shows green mucin image draining from a patulous, bulging papilla. The final diagnosis after right hepatectomy and bile duct resection was biliary IPMN associated with invasive carcinoma. (Courtesy S. Yeon Kim, MD.)
image
(Left) Axial CECT of a 75-year-old man shows mild left intrahepatic biliary ductal dilatation image. An ERCP performed previously reported a mucus “plug.”

image
(Right) Axial CECT of the same patient performed 6 years later shows marked left biliary ductal dilatation image, lobar atrophy, and calcifications image. Biliary IPMN and mucinous adenocarcinoma were identified at left hepatectomy. Biliary IPMN is a premalignant lesion and is considered a precursor for papillary cholangiocarcinoma.
image
Axial CECT of biliary IPMN reveals marked distended intrahepatic ducts with “aneurysmal” dilatation of the left intrahepatic duct image distended with mucin.

image
Axial gadolinium-enhanced GRE MR shows left bile duct IPMN with marked dilatation image.
image
Transverse US of left bile duct IPMN shows the distended bile duct with echogenic mucin image.

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