What are Pancreatic Cysts?
Pancreatic cysts are abnormal fluid-filled growths on or in the pancreas. There are several types of cysts, many of which are benign (non-cancerous) and some of which are associated with pancreatitis, or inflammation of the pancreas; please use the navigation on the left to access information about these different types. Cystic neoplasms of the pancreas include serous cystadenomas, mucinous cystadenomas, intraductal papillary mucinous neoplasm (IPMN), and cystically degenerated pancreatic neuroendocrine tumors. This section will review the work up, diagnosis and management of each of these types of pancreatic cysts.
With improved access to high quality abdominal imaging, pancreatic cysts are being diagnosed with increased frequency. Pancreatic cysts are identified in 1-2% of patients undergoing CT or MRI of the abdomen for an unrelated indication. Inflammatory cysts arise in the setting of pancreatitis.
Cystic Neoplasms of the Pancreas
There are several types of cystic tumors or neoplasms of the pancreas, each with malignant potential that varies from nearly zero to up to 70% depending on the type. Distinguishing a neoplasm from a pseudocyst and distinguishing among the different types of neoplasm is often straightforward, but at times can be challenging.
Although this type of cystic neoplasm is usually asymptomatic, it can cause pain. They can grow to be quite large, and some patients will have an abdominal mass easily observed upon physical examination. CT scan will reveal a cystic mass with a central scar and often with calcification. On endoscopic ultrasound, the tumor will be described as 'microcystic' or as having a 'honeycomb' appearance. Often it is difficult to remove the fluid from these cysts, because each individual compartment of the honeycomb is small. However, if fluid is sent for analysis, the CEA and amylase levels should be close to zero. Biopsy sent for cytology is generally non-diagnostic for these lesions.
Serous cystadenomas are benign tumors that harbor little if any potential to develop into a malignancy. For this reason, most centers (ours included) recommend observation. Surgery is indicated if these cysts become symptomatic or very large. Also, some patients opt to undergo surgical removal because of diagnostic uncertainty.
Most mucinous cystadenomas are asymptomatic, but they can cause pain. These tumors are most often seen in the tail of the pancreas of young women. Imaging will reveal a unilocular cyst (a cysts containing only one compartment), or one with a few septations (divisions causing multiple compartments within the cyst). If fluid is removed and sent for biochemical analysis (obtained by endoscopic ultrasound), the CEA will be high (over 192 ng/mL) and the amylase level will be low, because these cysts do not communicate with the pancreatic ductal system. Theses cysts do have the potential to become malignant (mucinous cystadenocarcinoma). Because these cysts are generally identified in young and otherwise healthy women and because of their malignant potential, the recommendation is for surgical removal. Because most of these cysts are found in the tail of the pancreas, most of these patients will need a distal pancreatectomy, which can be performed by a variety of techniques.
First described in the mid 1980's, IPMN is a cystic neoplasm of the pancreas that is being diagnosed with increasing frequency as an incidental finding on an MRI or CT scan of the abdomen done for some other indication. IPMN is a slow growing tumor that has malignant potential. Two distinct variants have been described: Main duct and Branch duct.
Main Duct IPMN
This variant of the disease may be asymptomatic, but often mirrors signs and symptoms of acute pancreatitis. On endoscopic evaluation, the ampulla of Vater (where the pancreatic duct meets the bile duct) is often described as having a "fishmouth" appearance, which is mucinous material being extruded from the pancreatic duct into the small intestine. It is the high viscosity of this mucinous fluid that obstructs the pancreatic duct and causes pancreatitis. A segment of the main pancreatic duct may be affected, or the disease may involve the entire main pancreatic duct. The rate of malignancy is very high (up to 70% in reported surgical series). For this reason, in medically fit patients, the recommendation is for surgical removal of the affected portion of the pancreas. If the entire duct is involved, the patient will need to have the entire pancreas removed (total pancreatectomy).
Branch Duct IPMN
Branch duct IPMN's are cystic neoplasms of the pancreas that have malignant potential. Many are asymptomatic and are identified on imaging studies done for another indication. However, these cysts can cause pancreatitis or jaundice. These cysts may be found in various locations throughout the gland and are seen with equal frequency in both genders. Great efforts are taken to distinguish branch duct IPMN's from serous and mucinous cystadenomas.
The management of branch duct IPMN's is challenging. The lifetime risk of one of these cysts becoming malignant is not entirely known and is difficult to determine. There is no medication to treat these cysts. Patients and their doctors are forced to choose between surveillance and surgical removal. Factors that contribute to this decision include the patient's age, presence or absence of symptoms, the size of the cyst, and whether or not there is a solid component or mural nodule. While surgical removal of these cysts will prevent the patient from developing pancreatic cancer from that cyst, pancreatic surgery is not without risk. The risk of the surgery must be carefully weighed against the risk of malignancy in making a determination about surgical removal versus surveillance.
Patients with the branch duct variant of IPMN generally can be safely observed if:
- The cyst is asymptomatic
- The cyst is less than 3 cm
- The cyst has no solid component or mural nodule
Acute pancreatitis is a clinical syndrome characterized by abdominal and back pain that may be associated with nausea, vomiting, and fever. Blood tests will reveal increased levels of pancreatic enzymes, and imaging studies (CT or MRI) will show inflammation in the pancreas and there may be fluid around the pancreas. These peripancreatic fluid collections may eventually become a pseudocyst. Pancreatic pseudocysts are pockets of fluid that are lined with either inflammatory or scar tissue. The vast majority of acute pancreatitis in the United States is caused by gallstones or alcohol. However, there are other less common causes such as medications (eg. thiazide diuretics), very elevated serum triglycerides, and rare genetic mutations.
Many pseudocysts will heal without treatment. Large and symptomatic pseudocysts however, may need to be drained. Internal drainage is the preferred method. In this procedure, once the pseuodcyst has matured (6 weeks following the onset of acute pancreatitis), it can be connected to the stomach or to a loop of bowel. This connection often can be achieved endoscopically (endoscopic cystgastrostomy or endoscopic cystenterostomy). When this is not feasible, the procedure can be performed surgically. External drainage is avoided if possible because it creates a connection between the pancreas and the skin that takes many months to heal. External drainage is reserved for patients that are too sick to undergo endoscopic or surgical drainage, often from an infection or worsening pancreatitis.