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).
Brach 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