The Kyoto guidelines are a classification system for intraductal papillary mucinous neoplasms (IPMNs) and mucinous cystic neoplasms (MCNs). They were first published in 2006, and revised guidelines were published in 2012 1, 2017 3, and 2024 4. They have been previously known as the Sendai criteria, the Tanaka criteria, and the Fukuoka consensus guidelines.
Contrast-enhanced CT and MRI have been shown to have comparable diagnostic performance for diagnosing malignant IPMN ref.
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Investigation
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cyst <5 mm
asymptomatic: invasive carcinoma is rare if the patient is asymptomatic, therefore, follow-up only is recommended
symptomatic: further evaluation or resection (clinical circumstances dictate)
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cyst >5 mm
pancreatic protocol CT or MRI pancreas and MRCP to evaluate
Classification
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main duct type IPMN
higher frequency of malignancy
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dilatation of the main duct >5 mm without other cause for obstruction
5-9 mm: "worrisome feature"
≥10 mm: "high-risk stigmata"
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branch duct type IPMN
cyst >5 mm communicating with the main pancreatic duct
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mixed type IPMN
appears like an advanced branch duct IPMN with main pancreatic duct dilatation (>5 mm)
higher frequency of malignancy, similar to the main duct type
High-risk stigmata
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enhancing solid component >5 mm
strongest association with malignant IPMN 5
main pancreatic duct ≥10 mm
Worrisome features
cyst ≥3 cm
thickened and enhancing cyst wall
enhancing mural nodule <5 mm
main pancreatic duct 5-9 mm
abrupt change in calibre of the pancreatic duct with distal pancreatic atrophy
cyst growth rate ≥2.5 mm/year.
elevated CA 19-9
clinical symptoms such as new onset of diabetes mellitus
Pathology
Histological subclassification
gastric-type: the majority of branch duct type IPMNs
intestinal-type
pancreaticobiliary-type
NB: The previously described oncocytic subtype has been classified as a separate entity to IPMN.
Treatment and prognosis
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resection
main duct type IPMNs
all other IPMNs with high-risk stigmata
all other mucinous cystic neoplasms
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cysts with worrisome features
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cysts ≥3 cm without worrisome features
if inconclusive, then close surveillance with alternating MRI and EUS every 3-6 months
strongly consider surgery in young patients
Cyst fluid analysis is optional in a centre with expertise in EUS fine-needle aspiration.
Surveillance
Optimal imaging surveillance strategies for suspected branch duct type IPMNs <3 cm and without worrisome features is unclear, but the yearly incidence of transformation to pancreatic cancer is estimated at 0.4-1.1% per year:
largest cyst <1 cm: CT or MRI/MRCP in 6 months, then every 2 years if no change
largest cyst 1-2 cm: CT or MRI/MRCP 6 monthly for 1 year, then yearly for 2 years, then lengthen interval up to 2 years if no change
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largest cyst 2-3 cm: EUS in 3-6 months, then lengthen interval up to 1 year alternating MRI with EUS as appropriate
consider surgery in young patients, with a need for prolonged surveillance
NB: The American Gastroenterological Association recommends stopping surveillance after 5 years if no significant change is observed or if a cyst is resected and found to be benign 2. This is not a recommendation that is explicitly stated in the Kyoto guidelines.