The pancreas is an elongated organ situated deep within the abdomen, positioned horizontally behind the stomach and in front of the spine. Its primary function is twofold: it produces digestive enzymes that flow into the small intestine to break down food, and it releases hormones like insulin and glucagon directly into the bloodstream to regulate blood sugar. A pancreatic cyst is an abnormal, fluid-filled sac that forms either on or within this gland. While a cyst simply refers to a fluid-filled lesion, the term encompasses a diverse group of growths. Most pancreatic cysts are non-cancerous, but some carry a risk of malignancy. Distinguishing between these types is the most important step in determining the appropriate next course of action.
Defining the Different Types of Pancreatic Cysts
Pancreatic cysts are broadly categorized into non-neoplastic and neoplastic. Non-neoplastic cysts arise from inflammation or injury, while neoplastic cysts originate from abnormal cell growth. The most common non-neoplastic type is the pseudocyst, which often forms following acute pancreatitis or abdominal trauma. Pseudocysts are not true cysts because they lack an epithelial cell lining, instead containing liquefied dead pancreatic tissue and a high concentration of digestive enzymes.
Neoplastic cysts include three main subtypes with different malignant potentials. Serous Cystadenomas (SCAs) are almost universally benign and rarely progress to cancer, often presenting as a collection of many small cysts with thin, clear fluid. In contrast, Mucinous Cystic Neoplasms (MCNs) and Intraductal Papillary Mucinous Neoplasms (IPMNs) are known as mucinous cysts because they produce thick, mucus-like fluid and are considered pre-malignant. MCNs are typically solitary, found in the body or tail of the pancreas, and occur almost exclusively in middle-aged women.
IPMNs are the most common type of potentially cancerous cyst and are unique because they grow within the pancreatic duct system itself. They are classified based on location, with Main Duct IPMNs (MD-IPMNs) carrying a significantly higher risk of cancer compared to Branch Duct IPMNs (BD-IPMNs). The specific characteristics of the fluid within these cysts can also aid in diagnosis, as mucinous cysts typically have high levels of a tumor marker called carcinoembryonic antigen (CEA).
Symptoms and How Cysts Are Discovered
Most pancreatic cysts are asymptomatic and are discovered incidentally during abdominal imaging, such as a CT scan or MRI. The detection of these lesions has increased, now found in up to 20% of the general population. Since most cysts are small and cause no issues, they remain unnoticed unless they begin to grow or cause obstruction.
When a cyst becomes symptomatic, the signs usually relate to its size and location within the pancreas. Abdominal pain, which may radiate to the back, is the most common symptom, occurring when the cyst presses on surrounding organs or nerves. Nausea and vomiting can also develop if a large cyst compresses the duodenum, the first part of the small intestine, delaying the passage of food.
A less frequent but more concerning symptom is jaundice, which may occur if a cyst in the head of the pancreas blocks the common bile duct. Initial diagnosis relies on cross-sectional imaging like MRI or CT to visualize the cyst and its internal features. If the cyst appears suspicious, an Endoscopic Ultrasound (EUS) may be performed, which uses a thin probe inserted into the digestive tract to provide a detailed view and collect a fluid sample for analysis.
Assessing Risk and Management Strategies
Once a pancreatic cyst is identified, the primary concern is assessing its risk of developing into pancreatic cancer. Risk stratification relies on identifying specific features visible on imaging, known as “worrisome features” or “high-risk stigmata.” Worrisome features include a cyst size of 30 millimeters or greater, a thickening of the cyst wall, or a moderate dilation of the main pancreatic duct, measuring between five and nine millimeters.
The presence of worrisome features usually prompts a more invasive evaluation, such as EUS with fluid sampling, to define the cyst type and screen for abnormal cells. High-risk stigmata suggest a high probability of cancer and include finding a solid, enhancing mural nodule measuring five millimeters or more. A main pancreatic duct dilation of 10 millimeters or greater, or the presence of obstructive jaundice, also fall into this high-risk category.
For cysts without these concerning features, such as Serous Cystadenomas or low-risk Branch Duct IPMNs, the recommended approach is active surveillance. This strategy involves regular follow-up imaging, typically with an MRI, scheduled every few months to a few years depending on the cyst’s size and baseline characteristics. The goal of surveillance is to monitor for any changes, such as rapid growth or the development of a solid component, that would indicate a progression in risk. Cysts that present with high-risk stigmata, or those that show progression during surveillance, are generally recommended for surgical resection to remove the lesion entirely.