Diagnostic Ultrasound - Abdomen and Pelvis

Intraductal Papillary Mucinous Neoplasm (IPMN)
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Diagnoses: Pancreas
PATHOLOGY
General Features
• Cystically dilated segment of pancreatic duct due to
intraluminal protrusion of papillary neoplastic epithelial
growth
Staging, Grading, & Classification
• Main duct type: Considered precursor to invasive pancreatic
ductal carcinoma
• Branch duct type: Generally benign with low malignancy
risk
• Mixed type: Behaves similar to main duct type
• Tanaka criteria (update to Sendai classification): Classifies
IPMN as high risk, worrisome, or low risk based on imaging
features in order to guide treatment decisions
○ High-risk stigmata: Obstructive jaundice with cystic lesion
at head of pancreas, enhancing solid component within
cyst, or MPD > 10 mm
○ Worrisome features: Largest cyst ≥ 3 cm,
thickened/enhancing cyst walls, MPD 5-9 mm,
nonenhancing mural nodule, or abrupt change in
diameter of MPD with parenchymal atrophy
○ Low risk: No worrisome features and largest cyst < 3 cm
○ Imaging findings direct towards interval follow-up, EUS,
or surgical resection
Gross Pathologic & Surgical Features
• MPD type: Mass or nodule in dilated mucin-filled duct
• SBD type: May be multifocal, lack of nodule formation,
contains inspissated mucin; may not see connection of
branch duct IPMN to MPD on gross specimen
Microscopic Features
• Histologically similar mucinous-type epithelium as seen with
mucinous cystic neoplasms but without ovarian-type
stroma
• Variable grades of dysplasia to gross invasion
○ MPD type: ~ 40% contain invasive carcinoma
○ SBD type: Most show no or low-grade dysplasia
• May see fibrotic atrophy of surrounding parenchyma due to
ductal obstruction
○ Can result in calcifying obstructive pancreatitis; however,
calcification does not usually involve tumor itself
CLINICAL ISSUES
Presentation
• Most common signs/symptoms
○ > 60% cystic pancreatic lesions found incidentally
○ May present with nonspecific symptoms of
nausea/vomiting, abdominal pain, weight loss, anorexia
• Other signs/symptoms
○ MPD type may result in pancreatitis from obstruction
secondary to excess mucin production
• Associations
○ Extrapancreatic malignancies, most commonly gastric or
colorectal carcinoma
○ Possibly greater prevalence of extensive SBD-type IPMN
after transplantation and immunosuppression
Demographics
• Age
○ Mean at diagnosis: 68 years; range: 60-80 years
• Gender
○ M > F
Natural History & Prognosis
• Overall 5-year survival for all patients with IPMN: ~ 60%
• Up to 70% of MPD type progress to invasive carcinoma
• SBD type often quiescent with low overall risk of
malignancy if < 3 cm
• Mixed type tends to behave similar to MPD type
• Long-term surveillance warranted even after resection
because of risk for multifocal disease: Synchronous and
metachronous
Treatment
• Imaging findings direct need for surgical resection, EUS, or
interval follow-up according to Tanaka criteria
• Surgical resection for all IPMN with high-risk features
○ Excellent 5-year survival in absence of invasive
component (94-100% vs. 40-60%)
○ Recurrence rate with invasive disease: 50-65% vs. < 8%
without
• If worrisome features present, EUS should be performed
for biopsy &/or aspiration
• If largest cyst > 3 cm with no other worrisome features
should also consider EUS
• If no associated concerning features, cyst size determines
follow-up intervals
○ < 1 cm: CT/MR in 2-3 years
○ 1-2 cm: CT/MR yearly for 2 years, then lengthen interval
if no change
○ 2-3 cm: Endoscopic ultrasound in 3-6 months, then
lengthen interval if no change, alternating MR and
endoscopic ultrasound
DIAGNOSTIC CHECKLIST
Image Interpretation Pearls
• Main duct type: Dilation of main pancreatic duct (> 5 mm)
without obstructive mass
• Branch duct type: Grape-like cluster of small cysts, with
communication to MPD
Reporting Tips
• Describe high-risk and worrisome features, including cyst
size, enhancing walls, MPD dilation, mural nodule, or abrupt
change in duct size with parenchymal atrophy
• Will require interval follow-up, EUS, or possible resection
based on associated features
SELECTED REFERENCES
1. Freeny PC et al: Moving beyond morphology: new insights into the
characterization and management of cystic pancreatic lesions. Radiology.
272(2):345-63, 2014
2. Kim JH et al: Intraductal papillary mucinous neoplasms with associated
invasive carcinoma of the pancreas: imaging findings and diagnostic
performance of MDCT for prediction of prognostic factors. AJR Am J
Roentgenol. 201(3):565-72, 2013
3. Tanaka M et al: International consensus guidelines 2012 for the
management of IPMN and MCN of the pancreas. Pancreatology. 12(3):183-
97, 2012
4. Gore RM et al: The incidental cystic pancreas mass: a practical approach.
Cancer Imaging. 12:414-21, 2012
5. Remotti HE et al: Intraductal papillary mucinous neoplasms of the pancreas:
clinical surveillance and malignant progression, multifocality and implications
of a field-defect. JOP. 13(2):135-8, 2012