Pancreatic Cysts

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GI NOTES

Pancreatic Cysts

Key points

Pancreatic cysts are common incidental findings, especially with age; most never become cancer.
The goal is to find the few mucinous cysts (IPMN and mucinous cystic neoplasm) that may progress, without over-treating the rest.
MRI with MRCP is the preferred imaging for characterizing and following cysts.
High-risk features (jaundice, solid component, enhancing mural nodule, main duct 10 mm or more, suspicious cytology) mean referral to a multidisciplinary pancreas team.
Endoscopic ultrasound with fine-needle aspiration is used when features are worrying or the diagnosis would change management.

1. Types of cyst

Cyst	Who and where	Malignant potential
Branch-duct IPMN	Older adults; communicates with the pancreatic duct	Low, rises with worrying features
Main-duct IPMN	Dilated main duct with mucin	High; usually surgical
Mucinous cystic neoplasm	Almost always women; body or tail; ovarian-type stroma	Moderate; resection usually advised
Serous cystadenoma	Older women; microcystic “honeycomb” with central scar	Very low; benign
Solid pseudopapillary neoplasm	Young women	Low-grade malignant; resect
Pseudocyst	After pancreatitis; not a true neoplasm	None

2. How to approach a new cyst

FIGURE: INCIDENTAL PANCREATIC CYST

Cyst found on imaging: characterize with MRI and MRCP

High-risk features
→ Multidisciplinary pancreas team, consider surgery

Worrisome features
→ EUS with fine-needle aspiration

Neither
→ Surveillance MRI, interval set by size

Original diagram summarizing the ACG 2018 and international consensus approaches.

High-risk features	Worrisome features
Obstructive jaundice from the cyst	Cyst 3 cm or larger
Enhancing solid component or mural nodule 5 mm or more	Mural nodule under 5 mm, thickened enhancing wall
Main pancreatic duct 10 mm or more	Main duct 5 to 9 mm, or abrupt duct caliber change with upstream atrophy
Suspicious or malignant cytology	Growth of 2.5 mm or more per year (some use 3 mm), raised CA 19-9, new diabetes, pancreatitis caused by the cyst

3. EUS and cyst fluid

CEA in cyst fluid above about 192 ng/mL suggests a mucinous cyst (it does not grade malignancy).
Low glucose (under about 50 mg/dL) is a sensitive marker of a mucinous cyst.
Amylase very high suggests a pseudocyst or duct communication.
Cytology is specific but often has too few cells; molecular markers (KRAS and GNAS for IPMN, TP53 and others for advanced lesions) add accuracy.
Thread-like viscous fluid (“string sign”) supports mucin.

4. Surveillance (presumed IPMN or MCN, no worrying features; ACG 2018)

Cyst size	First 2 years	If stable
Under 1 cm	MRI every 2 years	Lengthen intervals
1 to 2 cm	MRI yearly for 3 years	Every 2 years for 4 years
2 to 3 cm	MRI or EUS every 6 to 12 months for 3 years	Yearly for 4 years
Over 3 cm	Refer to a multidisciplinary team	Alternate MRI and EUS every 6 months

Only survey patients who would be fit for surgery; stop when they no longer are.
A cyst stable for 5 years or more may allow surveillance to stop in some patients, though guidance varies.
Serous cystadenomas and pseudocysts do not need cancer surveillance.

Self-check questions

Which imaging test is preferred for following a pancreatic cyst?
A 1.5 cm branch-duct IPMN has no worrying features. What is the plan?
Cyst fluid CEA is 450 ng/mL. What does this suggest?
Name two high-risk features.

Answers: (1) MRI with MRCP. (2) MRI yearly for 3 years, then every 2 years if stable. (3) A mucinous cyst; it does not tell you whether it is malignant. (4) Any two of: jaundice, enhancing solid component, main duct 10 mm or more, suspicious cytology.

References

Elta GH, Enestvedt BK, Sauer BG, Lennon AM. ACG Clinical Guideline: Diagnosis and Management of Pancreatic Cysts. Am J Gastroenterol. 2018;113(4):464-479.
Ohtsuka T, Fernandez-del Castillo C, Furukawa T, et al. International evidence-based Kyoto guidelines for the management of intraductal papillary mucinous neoplasm of the pancreas. Pancreatology. 2024;24(2):255-270.
Vege SS, Ziring B, Jain R, Moayyedi P, et al. American Gastroenterological Association Institute guideline on the diagnosis and management of asymptomatic neoplastic pancreatic cysts. Gastroenterology. 2015;148(4):819-822.
European Study Group on Cystic Tumours of the Pancreas. European evidence-based guidelines on pancreatic cystic neoplasms. Gut. 2018;67(5):789-804.

For educational purposes only. This note does not replace clinical judgment or local protocols. Check doses against current labeling and institutional guidance.