Gastroenterologists and surgeons are increasingly being asked to consult on patients who are discovered to have a pancreatic cyst. In most instances, the cyst is discovered on an imaging study such as an abdominal ultrasound or abdominal CT scan that was requested for symptoms unrelated to the pancreas. Occasionally, the cyst is discovered on an imaging study for mild abdominal symptoms caused by a cyst.

One common cyst is called a pancreatic pseudocyst. This is an encapsulated collection of fluid that can occur as a result of either acute or chronic pancreatitis. As such, almost all patients have had severe abdominal pain in the past and many have been hospitalized for this pain.

Another common cyst within the pancreas is a cystic tumor. There are many types of cystic tumors. One is termed a serous cystadenoma. Serous cystadenomas are almost always benign and remain benign. Another cystic tumor is termed a mucinous cystic tumor. Some are benign and others are or may become malignant. At times, abdominal CT scan or magnetic resonance imaging (MRI) of the pancreas can help distinguish a serous cystadenoma from a mucinous cystic tumor or a pseudocyst. Increasingly, we now rely on the characteristics of the fluid to help distinguish a mucinous tumor from a serous cystadenoma and pseudocyst. Fluid can be aspirated by a radiologist who is trained to insert a needle under CT guidance through the skin directly into the cyst itself. Fluid can also be aspirated by endoscopists who are trained in the technique of endoscopic ultrasound (EUS) and the insertion of a needle through either the wall of the stomach or the duodenum. The fluid can be analyzed for cytology, CEA, and other tumor markers as well. If the characteristics of the fluid are indicative of a mucinous neoplasm, most patients then undergo surgery to remove the portion of the pancreas that contains this tumor because it is either already malignant or may become malignant in the future. A pseudocyst or a serous cystadenoma that is causing no symptoms does not require removal.

In addition to these cystic structures, there are a variety of other cystic tumors of the pancreas that take origin from the islet cells, acinar cells, ductal cells, and blood vessels. Cysts are also associated with polycystic renal disease, Von Hippel-Lindau disease, and echinococcal disease (caused by a parasite).

One cystic process originating from ductal cells is called intraductal papillary mucinous tumor. This consists of tumor cells originating from the ducts themselves that secrete a mucinous material which can plug up the ducts and appear cystic on an imaging study. This tumor is considered to be pre-malignant (if not already malignant), and surgery is generally recommended to remove it.

Peter Banks, M.D. Director, Clinical Gastroenterology Service Brigham & Women's Hospital Professor of Medicine Harvard Medical School