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Intraductal Papillary Mucinous Neoplasm
Classified as main duct, combined, or branch duct type
Clinical Issues
• 20-50% of resected cystic pancreatic tumors
Incidence increasing due to increased incidental detection on imaging for other reasons
• Most patients are asymptomatic
Symptoms associated with intermittent pancreatic ductal obstruction by tenacious mucin &/or low-grade pancreatitis
• Average age at presentation: Mid 60s
• Prognosis better than conventional ductal adenocarcinoma
Noninvasive tumors: 5-year survival rate: > 75%
Invasive tumors: 5-year survival rate: 34-62%
– Significantly better than pancreatic ductal adenocarcinoma
Invasive components may be very focal, requiring submission of entire lesion
• Surgical resection treatment of choice
Vast majority surgically resectable
Macroscopic
• Most common in pancreatic head
• Often involve only portion of pancreatic duct but may be multifocal or involve entire duct
Microscopic
• Composed of flat or papillary mucinous epithelium
• 4 epithelial subtypes
Gastric
Intestinal
Pancreatobiliary
Oncocytic
• 2-tiered dysplasia grading system (low- vs. high-grade dysplasia)
Main Duct IPMNThe markedly dilated main pancreatic duct contains nodular mucosa and abundant mucin (stained with yellow dye). The ampullary orifice is indicated . A dilated patulous ampulla with extruded mucin is a typical appearance of this tumor on endoscopy.
Branch Duct IPMNGross photo shows a small cyst with a smooth lining connected to the main pancreatic duct via a dilated branch duct .
Mixed Main Duct and Branch Duct TumorH&E shows an intraductal neoplastic papillary epithelial proliferation in both the main duct and a large branch duct . The stroma is dense and fibrotic.
Invasive AdenocarcinomaInvasive tubular adenocarcinoma arising in association with intraductal papillary mucinous neoplasm (IPMN) is shown. The main duct contains intermediate- to high-grade dysplastic epithelium . The infiltrating neoplastic glands are of pancreatobiliary type.
TERMINOLOGY
Abbreviations
• Intraductal papillary mucinous neoplasm (IPMN)
Definitions
• Grossly visible, mucin-producing epithelial neoplasm present within main pancreatic duct &/or its branches
• Subclassification based on duct(s) involved
Main duct type
– Mucinous epithelium confined to main pancreatic duct
Combined type
– Mucinous epithelium involving both main duct and branch ducts
Branch duct type
– Mucinous epithelium confined to branch ducts
ETIOLOGY/PATHOGENESIS
Molecular Features
• DPC4/SMAD4 loss uncommon, in contrast to high-grade PanIN and invasive ductal adenocarcinoma
• Overexpression of EGFR and ERBB2 common
• KRAS mutations common except for oncocytic type
• Loss of p16 increases with grade of dysplasia
Risk Factors
• History of diabetes
• Family history of pancreatic ductal adenocarcinoma (associated with branch duct IPMN)
CLINICAL ISSUES
Epidemiology
• Incidence
20-50% of resected cystic pancreatic tumors
– Incidence increasing due to increased incidental detection on imaging for other reasons
– Prevalence in general population estimated to be as high as 13.5% based on imaging studies
• Age
Range: 25-94 years
– Average: Mid 60s
• Sex
Slightly more common in men but varies according to ethnicity
Presentation
• Most patients asymptomatic
• Symptomatic patients usually present with vague complaints related to duct obstruction/low-grade pancreatitis
Abdominal &/or back pain
Anorexia
Weight loss
• Symptoms often present for months to years before diagnosis established
Endoscopic Findings
• Mucin extravasation from patulous ampulla of Vater in ∼ 25% of cases, essentially diagnostic of intestinal-type IPMN
Treatment
• Surgical resection is treatment of choice
80-98% of IPMNs are surgically resectable
Prognosis
• Noninvasive tumors: 5-year survival rate: > 75%
• Invasive tumors: 5-year survival rate is significantly lower (34-62%) than for noninvasive tumors
Still significantly better than that of conventional pancreatic ductal adenocarcinoma
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contains nodular mucosa and abundant mucin (stained with yellow dye). The ampullary orifice is indicated 
. A dilated patulous ampulla with extruded mucin is a typical appearance of this tumor on endoscopy.
connected to the main pancreatic duct 
via a dilated branch duct 
.
and a large branch duct 
. The stroma is dense and fibrotic.
. The infiltrating neoplastic glands 
are of pancreatobiliary type.
