Intraductal Papillary Mucinous Neoplasm

 Classified as main duct, combined, or branch duct type






Clinical Issues




• 20-50% of resected cystic pancreatic tumors
image Incidence increasing due to increased incidental detection on imaging for other reasons

• Most patients are asymptomatic
image 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
image Noninvasive tumors: 5-year survival rate: > 75%

image Invasive tumors: 5-year survival rate: 34-62%
– Significantly better than pancreatic ductal adenocarcinoma

image Invasive components may be very focal, requiring submission of entire lesion

• Surgical resection treatment of choice
image 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

image Gastric

image Intestinal

image Pancreatobiliary

image Oncocytic

• 2-tiered dysplasia grading system (low- vs. high-grade dysplasia)

image
Main Duct IPMN
The markedly dilated main pancreatic duct image contains nodular mucosa and abundant mucin (stained with yellow dye). The ampullary orifice is indicated image. A dilated patulous ampulla with extruded mucin is a typical appearance of this tumor on endoscopy.


image
Branch Duct IPMN
Gross photo shows a small cyst with a smooth lining image connected to the main pancreatic duct image via a dilated branch duct image .

image
Mixed Main Duct and Branch Duct Tumor
H&E shows an intraductal neoplastic papillary epithelial proliferation in both the main duct image and a large branch duct image. The stroma is dense and fibrotic.

image
Invasive Adenocarcinoma
Invasive tubular adenocarcinoma arising in association with intraductal papillary mucinous neoplasm (IPMN) is shown. The main duct contains intermediate- to high-grade dysplastic epithelium image. The infiltrating neoplastic glands image 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

image Main duct type

– Mucinous epithelium confined to main pancreatic duct

image Combined type

– Mucinous epithelium involving both main duct and branch ducts

image 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
image 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
image Range: 25-94 years
– Average: Mid 60s

• Sex
image 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

image Abdominal &/or back pain

image Anorexia

image 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
image 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

image Still significantly better than that of conventional pancreatic ductal adenocarcinoma

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Apr 20, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Intraductal Papillary Mucinous Neoplasm
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