Kyoto guidelines

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. 

Investigation

• 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)

• cyst >5 mm

  • pancreatic protocol CT or MRI pancreas and MRCP to evaluate

Classification

• main duct type IPMN

  • higher frequency of malignancy

  • dilatation of the main duct >5 mm without other cause for obstruction

    • 5-9 mm: "worrisome feature"

    • ≥10 mm: "high-risk stigmata"

• branch duct type IPMN

  • cyst >5 mm communicating with the main pancreatic duct

• 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

• enhancing solid component >5 mm

  • strongest association with malignant IPMN ⁵

• main pancreatic duct ≥10 mm

• obstructive jaundice

Worrisome features

• cyst ≥3 cm

• thickened and enhancing cyst wall

• enhancing mural nodule <5 mm

• main pancreatic duct 5-9 mm

• lymphadenopathy

• abrupt change in caliber 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

• acute pancreatitis

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

• resection

  • main duct type IPMNs

  • all other IPMNs with high-risk stigmata

  • all other mucinous cystic neoplasms

• endoscopic ultrasound (EUS)

  • cysts with worrisome features

  • 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 center 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

• 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.