2007

Managing Incidentally Found Pancreatic Cystic Lesions: Identifying Cases Suited for Resection

Points to Remember

• The pancreatic cysts that are seen most commonly in elderly patients arise from side branches of the main pancreatic duct. They are conceptually analogous to colon polyps — benign tumors (adenomas) that have the potential to become malignant over time.
• Unlike colon polyps, which can be removed during colonoscopy, removal of branch duct lesions requires resection of the pancreas.
• Cysts smaller than 15 mm with an undilated main pancreatic duct are generally followed conservatively with imaging studies.
• Cysts measuring 15 to 20 mm, those associated with main pancreatic dilation, and those causing symptoms warrant clinical attention at a multidisciplinary specialty center with demonstrated excellence in managing diseases of the pancreas.

The Challenge

As imaging technology improves and abdominal scans become more frequent, an increasing number of pancreatic cysts are being detected by MRI and CT scans that are incidental to the original intent of the imaging studies. This is particularly true in patients aged 60 years or older. Autopsy studies, retrospective reviews, and Mayo Clinic Pancreas Clinic data all suggest that small cysts are common, occurring in approximately 1 in 5 elderly patients.

Most pancreatic cysts are not cancerous but have malignant potential. Therefore, cystic lesions incidentally found need to be carefully evaluated. They pose management challenges because knowledge of how to respond to them is evolving so rapidly that it is not well disseminated beyond pancreas specialists. Management of pancreatic cystic lesions benefits from a multidisciplinary team approach that integrates specialists from surgery, gastroenterology, radiology, pathology, and cytology, all of whom have subspecialty interest in pancreatic disease. Comprehensive evaluation includes imaging by CT, MRI, and endoscopic ultrasound (EUS) sampling for greater visualization and to assess cell types.

Risk Stratification

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Various types of cysts may be found in the pancreas, with or without symptoms such as abdominal pain or pancreatitis (Table). Therefore, the first goal of pancreatic cyst management is to identify patients who can safely be followed and to recommend for surgery only patients whose risk of malignancy is high. Patients with symptoms (pancreatitis) and findings on cross-sectional imaging can help with initial risk stratification. Incidentally identified cysts smaller than 15 mm that are not associated with main pancreatic duct dilation can be followed with yearly CT scans. Cysts larger than 15 mm up to 20 mm, those associated with pancreatitis, and those with dilation of the main pancreatic duct warrant clinical attention.

MRI showing pancreatic cyst. Cystic tumor in the head of the pancreas with a solid component (arrow). Such cysts need further evaluation for consideration for surgery.

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CT showing low-risk pancreatic cyst. This pseudocyst (arrow) resulted from an attack of gallstone pancreatitis. Since it was symptomatic (with abdominal pain, early satiety, and vomiting), it was successfully drained endoscopically.

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The most common cyst found incidentally is an intraductal papillary mucinous neoplasm (IPMN), which is a mucin-producing premalignant tumor. Pancreatic pseudocysts result from pancreatitis and do not progress to malignancy (Figures 1 and 2).

Care of Patients With Pancreatic Cysts

If an initial scan reveals cystic lesions, Mayo Clinic specialists recommend the following steps:

1. Repeat a high-resolution pancreas protocol CT scan or an MRI to get the best image quality.
2. Recognize high-risk lesions, such as cysts with a notable solid component and cysts associated with main pancreatic duct dilation. These cysts have a high risk of being malignant and warrant immediate referral to a specialty center for further evaluation with EUS and surgical assessment.

3. In patients with pancreatitis, distinguish between a pseudocyst due to pancreatitis and mucinous cysts causing pancreatitis. This requires careful review of images to determine if a cyst was present before development of pancreatitis (mucinous tumor) or followed an attack of pancreatitis (pseudocyst). If in doubt, further radiologic evaluation by EUS and cyst fluid sampling may be required.