Prevention: Pancreatic Cyst Surveillance Program
The ubiquity and availability of high resolution cross sectional imaging (CT and MRI) of the abdomen has allowed physicians to identify many patients with cystic tumors of the pancreas. Many of these benign cysts have the potential to become cancer, and early intervention presents an opportunity to prevent a lethal malignancy. While some of these cysts will require surgical removal, many can be safely observed with serial imaging studies and endoscopic ultrasound. The decision to recommend surgical removal is a complex undertaking that must factor in many variables so that nothing is overlooked and surveillance studies are not missed. Keeping track of the unique dataset of each patient and prescribe an individualized program of surveillance is best accomplished by a multidisciplinary team of care providers dedicated to the management of cystic tumors of the pancreas.
The Winthrop Pancreatic Cyst Surveillance Program team meets weekly on Wednesday mornings to discuss patients presenting with new pancreatic cysts and to review the follow-up data on our existing registry of patients. Team members from surgery, gastroenterology, biliary endoscopy, oncology and genetics each offer their unique and specialized perspective to come to a multidisciplinary consensus plan of management of each of our patients.
A cyst (fluid filled cavity) of the pancreas may be either inflammatory caused by pancreatitis, or neoplastic (a tumor).
Pseudocyst: Inflammatory cysts of the pancreas are called pseudocysts because they do not have a true cyst lining. These fluid-filled structures within or around the pancreas are the result of severe pancreatitis that resulted in a disruption of the pancreatic ductal system and leakage of pancreatic fluid. Over a period of several weeks, the body encapsulates the fluid within a dense fibrous capsule creating the pseudocyst. Pseudocysts are not tumors and they do not have the potential to become cancer. Many of these cysts will resolve with time, however, some will continue to enlarge and may be symptomatic. Persistent and symptomatic pseudocysts will require a drainage procedure. This was traditionally accomplished surgically by performing a cystgastrostomy, but most patients can now undergo an endoscopic cystgastrostomy and avoid surgery altogether.
Cystic neoplasms or tumors of the pancreas include serous cystadenoma, mucinous cystadenomas, and intraductal papillary mucinous neoplasms (IPMN) which have two variants: branch duct and main duct. Occasionally, pancreatic neuroendocrine tumors will undergo cystic degeneration and present as a cyst. Pseudopapillary epithelial neoplasms (SPEN or Frantz’s tumor) can also appear cystic on imaging.
Serous cystadenoma: These are benign cysts that have no malignant potential. They can grow to be quite large and can even present as a palpable abdominal mass. On imaging, these cysts demonstrate multiple small compartments and are often describe as having a ‘honeycomb’ appearance. On CT scan, the radiologist will often see a central scar and calcification. If fluid is obtained from the cyst during an endoscopic ultrasound, the cyst fluid amylase and CEA will both be low. Cytology is usually nondiagnostic and the aspirate is often described as bloody.
Because these cysts have no malignant potential, most are simply observed. Because there is some diagnostic overlap between serous and mucinous cysts based on the available testing, we do recommend yearly surveillance of these cysts by cross sectional imaging. There is no known medial therapy. Surgery is reserved for patients where the cyst is causing symptoms, which typically involves abdominal pain.
Mucinous Cystadenoma: These are benign cysts that harbor malignant potential. They typically occur in young and middle age women and these tumors are most often found in the tail of the pancreas. On imaging, these cysts are unilocular or have just a few septae. These cysts generally do not communicate with the main pancreatic ductal system, so the fluid amylase will be low. There is, however, a true mucinous cyst lining, so the fluid CEA would be expected to be high (greater then 192). Cytology may demonstrate neoplastic cells with papillary features and the aspirate may stain positive for mucin.
Because these cysts harbor the potential to become malignant, are often found in young otherwise healthy women, and are typically located in the tail of the pancreas, the general recommendation is to proceed with surgical removal which typically requires a distal pancreatectomy. On final pathology, these cysts will exhibit ovarian- like stroma.
Branch duct IPMN
These are benign cysts that harbor malignant potential. The malignant potential varies widely based on a number of characteristics of the cyst and the patient, but multiple surgical series have found a malignancy rate of 20 to 25% when these tumors are removed. These tumors have no predilection for site within the pancreas or gender of the patient. On imaging, these cysts are unilocular or have just a few septae. By definition, these cysts communicate with the main pancreatic ductal system, so the fluid amylase will be high. As with the mucinous cystadenomas, there is a true mucinous cyst lining, so the fluid CEA would be expected to be high (greater then 192). Cytology may demonstrate neoplastic cells with papillary features and the aspirate may stain positive for mucin.
Asymptomatic cysts less than 3 cm that harbor no solid component (mural nodule) generally can be safely observed. These cysts do have malignant potential, requiring lifelong surveillance. Patients with cysts less than 1 cm generally undergo biannual surveillance imaging with MRI. As the cyst size increases, surveillance intervals shorten and many patients will be referred for endoscopic ultrasound. These recommendations are tailored to the individual data set of each patient and depend on many factors including, but not limited to, the gender, age, smoking history and family history of the patient.
Data from multiple series have demonstrated that independent risk factors for malignancy include male gender, increasing age, presence of symptoms or a mural nodule, and cyst size over 3 cm. Therefore, surgical removal is generally recommended in medically fit patients with symptoms, cysts over 3 cm, or cysts harboring a solid component (mural nodule).
Main duct IPMN: The main pancreatic ductal system itself may become IPMN. This will appear as a dilation of the pancreatic duct which can be either segmental or diffuse (involving the entire duct). Upper endoscopy will reveal a ‘fishmouth’ appearance of the ampulla of vater which is mucin being extruded out of the duct and into the lumen of the small intestine. Pancreatoscopy will reveal papillary projections that are often describes as ‘fish eggs.’ Fluid aspirated from the duct will have a high amylase and a high CEA. The viscous mucin produced by the main pancreatic duct not uncommonly causes pancreatitis and its associated pain, but it may be asymptomatic.
In surgical series, the rate of malignancy in the main duct variant of IPMN is as high as 70%. For this reason, surgical removal of the affected portion of the duct is generally recommended. This may require a total pancreatectomy (removal of the entire pancreas), which is a life altering, but potentially life-saving intervention.