Intraductal papillary mucinous neoplasm is a type of tumor that grows within the pancreatic
ducts and is characterized by the production of thick fluid by the tumor cells.
Intraductal papillary mucinous neoplasms are important because if they are left untreated
some of them progress to invasive cancer.
Just as colon polyps can develop into colon cancer if left untreated, so too do some intraductal
papillary mucinous neoplasms progress into an invasive pancreatic cancer.
Intraductal papillary mucinous neoplasms can present an opportunity to treat a pancreatic
tumor before it develops into an aggressive, hard-to-treat cancer.
History In 1982, IPMN was reported as a "mucin-producing
tumor" by Kazuhiko Ohashi of the Japanese Foundation for Cancer Research.
Classification Pathologists classify intraductal papillary
mucinous neoplasms into two broad groups - those that are associated with an invasive cancer
and those that are not associated with an invasive cancer.
This separation has critical prognostic significance.
Patients with a surgically resected intraductal papillary mucinous neoplasm without an associated
invasive cancer have an excellent prognosis, while patients with a surgically resected
intraductal papillary mucinous neoplasm with an associated invasive cancer have a worse
prognosis.
Intraductal papillary mucinous neoplasms without an associated invasive cancer can be further
subcategorized into three groups.
They are IPMN with low-grade dysplasia, IPMN with moderate dysplasia, and IPMN with high-grade
dysplasia.
This categorization is less important than the separation of IPMNs with an associated
cancer from IPMNs without an associated invasive cancer, but this categorization is useful
as IPMNs are believed to progress from low-grade dysplasia to moderate dysplasia to high-grade
dysplasia to an IPMN with an associated invasive cancer.
Diagnosis
Intraductal papillary mucinous neoplasms can come to clinical attention in a variety of
different ways.
The most common symptoms include abdominal pain, nausea and vomiting.
The most common signs patients have when they come to medical attention include jaundice,
weight loss, and acute pancreatitis.
These signs and symptoms are not specific for an intraductal papillary mucinous neoplasm,
making it more difficult to establish a diagnosis.
Doctors will therefore often order additional tests.
Once a doctor has reason to believe that a patient may have an intraductal papillary
mucinous neoplasm, he or she can confirm that suspicion using one of a number of imaging
techniques.
These include computerized tomography, endoscopic ultrasound, and magnetic resonance cholangiopancreatography.
These tests will reveal dilatation of the pancreatic duct or one of the branches of
the pancreatic duct.
In some cases a fine needle aspiration biopsy can be obtained to confirm the diagnosis.
Fine needle aspiration biopsy can be performed through an endoscope at the time of endoscopic
ultrasound, or it can be performed through the skin using a needle guided by ultrasound
or CT scanning.
IPMN forms cysts in the pancreas.
These cysts are visible in CT scans.
However, many pancreatic cysts are benign.
A growing number of patients are now being diagnosed before they develop symptoms.
In these cases, the lesion in the pancreas is discovered accidentally when the patient
is being scanned for another reason.
Up to 6% of patients undergoing pancreatic resection did so for treatment of incidental
IPMNs.
Scientists at the Sol Goldman Pancreatic Cancer Research Center at Johns Hopkins reported
in the July 20, 2011 issue of Science Translational Medicine that they have developed a gene-based
test that can be used to distinguish harmless from precancerous pancreatic cysts.
The test may eventually help patients with harmless cysts avoid needless surgery.
Bert Vogelstein and his colleagues discovered that almost all of the precancerous cysts
of the pancreas have mutations in the GNAS and/or the GNAS gene.
The researchers then tested a total of 132 intraductal papillary mucinous neoplasms for
mutations in KRAS and GNAS.
Nearly all had mutations in GNAS, KRAS or both.
Next, the investigators tested harmless cysts such as serous cystadenomas, and the harmless
cysts did not have GNAS or KRAS mutations.
Larger numbers of patients must be studied before the gene-based test can be widely offered.
Treatment The treatment of choice for main-duct IPMNs
is resection due to approximately 50% chance of malignancy.
Side-branch IPMNs are occasionally monitored with regular CT or MRIs, but most are eventually
resected, with a 30% rate of malignancy in these resected tumors.
Survival 5 years after resection of an IPMN without malignancy is approximately 80%, 85%
with malignancy but no lymph node spread and 0% with malignancy spreading to lymph nodes.
Surgery can include the removal of the head of the pancreas, removal of the body and tail
of the pancreas, or rarely removal of the entire pancreas.
In selected cases the surgery can be performed using minimally invasive techniques such as
laparoscopy or robotic surgery.
See also Pancreatic mucinous cystic neoplasm
Pancreatic serous cystadenoma Solid pseudopapillary neoplasm
References
External links The Toronto Video Atlas of Liver, Pancreas
and Transplant Surgery – Video of Whipple procedure in IPMN case