Intraductal papillary mucin producing neoplasms: diagnosis and management

Intraductal papillary mucin producing neoplasms (IPMN) have 3 forms: main-duct type, branch-type and combined according to the ductal changes: a cystically dilated branch duct as branch-type IPMN and a remarkably dilated main pancreatic duct with or without cystically dilated brach-ducts as main-duct type IPMN and a combination of the two forms. The branch-type IPMN is mostly benign but it can be multifocal in 30% and relapsing after resection in 10%. Invasion should be suspected in 15% mainly in symptomatic patients with cystic lesion of >3 cms, mural nodules and main-duct dilation of >10mm. The main-duct or combined IPMN is malignant in 70% and invasive in 43% at the diagnosis. Malignancy is indicated by duct dilation of >15mm, mural nodules and clinical symptoms. MRCP followed by ERCP or EUS with intraductal biopsy and/or cytology are the method of choice to diagnose these early tumors but K-ras mutation with microsatellite instability may be necessary to differentiate between adenoma and in situ cancers.

Patients and results: In the last 5 years we have diagnosed 16 cases of IPMN. There were 13 main-duct type and 2 branch-type and 1 mixed type tumors demonstrated by ERCP. Intraductal cytology was positive in 8, intraductal biopsy in 8 and both in 4 cases. Resection confirmed an invasive cancer in 4 cases, adenoma in 1 biliary IPMN, but diagnosed only pancreatitis in 6 cases although thorough follow-up and/or autopsy demonstrated stable or progressive IPMN in 5 of them. No operation was performed in 5 patients because of inappropriate performance status. Pre-, and postoperative histology or cytology agreed in only 3 cases.

Conclusion: IPMN can be diagnosed with ERCP and intraductal cytology and/or biopsy rather accurately but close cooperation is necessary between the endoscopist, radiologist, pathologist and surgeon to prevent invasion of the premalignant forms at due time.