Pancreatic cysts are fluid-filled growths that develop on or in the pancreas, an organ located behind the stomach. While finding a growth on the pancreas can understandably cause concern, many of these cysts are benign and do not pose a significant threat. Understanding their characteristics and potential is important for proper evaluation and management.
Malignancy Risk of Pancreatic Cysts
The percentage of pancreatic cysts that are cancerous is not a single, fixed number, as it varies considerably based on the cyst’s type and other features. The vast majority of pancreatic cysts are non-cancerous. Less than 1% of all pancreatic cysts are cancerous at the time of discovery.
However, up to 30% of pancreatic cysts have the potential to become cancerous over time, although this progression is typically slow. It is important to note that even among precancerous cysts, only a small percentage will ultimately develop into cancer. For example, the annual risk of malignancy for intraductal papillary mucinous neoplasms (IPMNs) and mucinous cystic neoplasms (MCNs) when identified is about 0.25%.
Types of Pancreatic Cysts
Pancreatic cysts are categorized based on their cellular makeup and potential for malignancy. Pseudocysts are the most common type of pancreatic cyst and are usually benign, often forming as a result of pancreatitis, which is inflammation of the pancreas. These are not true cysts as they are lined by scar or inflammatory tissue rather than epithelial cells. Serous cystadenomas (SCAs) are another common type, characterized by thick, fibrous walls and clear fluid. SCAs are almost always benign, though they can grow large enough to cause symptoms.
Other types of cysts carry a higher potential for malignancy. Intraductal Papillary Mucinous Neoplasms (IPMNs) are the most frequently encountered precancerous cysts, originating in the pancreatic ducts and producing mucus. IPMNs can be found in the main pancreatic duct (main-duct IPMN) or in the smaller side branches (branch-duct IPMN), with main-duct IPMNs having a greater risk of becoming cancerous. Mucinous Cystic Neoplasms (MCNs) are another type of precancerous cyst, almost exclusively affecting women, typically in their 40s and 50s. MCNs are usually found in the body or tail of the pancreas and, while often benign initially, have the potential for malignant transformation. Less than 20% of MCNs are cancerous. Rare malignant cysts, such as cystic pancreatic neuroendocrine tumors (PNETs), also exist.
Factors Influencing Malignancy Risk
Several characteristics and clinical indicators influence the likelihood of a pancreatic cyst being or becoming malignant. Cyst size is a contributing factor, with larger cysts often correlating with a higher risk. Cysts smaller than 15 mm are almost always non-cancerous. Cysts larger than 3 centimeters have a greater likelihood of malignancy. A rapid increase in cyst size, defined as 2.5 mm or more per year, can also indicate a higher risk of malignancy.
The presence of symptoms, such as new abdominal pain, nausea, vomiting, or unexplained weight loss, can be a warning sign, although many cysts, even those with malignant potential, are asymptomatic. Imaging findings like a solid component or nodule within the cyst raise concern, as solid cysts are three times more likely to be cancerous than those without solid components. Dilation of the main pancreatic duct, especially if it measures 2.5 mm or more, is another indicator that can predict the development of pancreatic cancer, particularly when combined with a cyst. A family history of pancreatic cancer or certain genetic syndromes can also increase an individual’s risk.
Managing Pancreatic Cysts
Once a cyst is identified, diagnostic tools are used to assess its nature. Imaging techniques such as CT scans, MRI, and magnetic resonance cholangiopancreatography (MRCP) provide detailed views of the cyst. An endoscopic ultrasound (EUS) with fine needle aspiration (FNA) may be used to obtain fluid or tissue samples for analysis, helping to determine if cancer cells are present.
For cysts deemed low-risk, a strategy of watchful waiting with periodic imaging surveillance is often recommended. The goal of this surveillance is to monitor for any changes in the cyst’s size or characteristics that might suggest progression. If a cyst develops worrisome features or causes symptoms, intervention may be necessary. Surgical removal is the primary treatment option for high-risk or symptomatic cysts, aiming to remove the cyst and potentially part of the pancreas. Given the complexities, consulting a medical professional is important to assess individual risk and to develop a personalized management plan.