Pancreatic Pathology Online
Pathology of Intraductal Papillary Mucinous Tumour of the Pancreas
These include a
group of tumours characterized by :
(i) Intraductal neoplastic papillary proliferations;
(ii) Abundant mucin secretion;
(iii) Cystic duct dilatation;
In terms of histologic and biologic behavior, three basic types are as follows:
(i) A benign intraductal papillary mucinous adenoma;
(ii) A borderline intraductal papillary mucinous tumour with moderate dysplasia;
(iii) An obviously malignant intraductal papillary mucinous carcinoma.
These tumors account for about 1% to 2% of exocrine pancreatic neoplasms.
Site: Most tumours arise in the head of the pancreas.
Clinical presentation: Patients tend to have pancreatitis-like symptoms for years.
They affect predominantly males (average age 60).
Gross features: Grossly, most of the tumours cause cystic dilatation of a portion of the main pancreatic duct or of one of its branches.
Diffuse involvement of the entire pancreatic duct system may also occur.
Papillary proliferations may not be apparent in tumours having large secretion of mucin.
The tumors show papillary proliferations of columnar mucus-secreting epithelial cells replacing the normal duct epithelium.
Scattered goblet cells, Paneth cells and endocrine cells may be occasionally present.
An oncocytic variant has recently been reported.
Benign intraductal papillary mucinous adenomas show a simple papillary or villous growth pattern and there is no cellular atypia.
Borderline variants show an irregular papillary growth with moderate epithelial dysplasia and frequent mitoses.
In intraduct papillary mucinous carcinoma the papillary proliferations show marked irregularity, cribriform gland formation, and marked nuclear abnormalities.
According to its invasiveness two subtypes are:
(i) Non-invasive - Tumour remains confined to the duct system.
(ii) Invasive - Tumour invades the surrounding pancreatic tissue.
Invasive component may resemble either ductal adenocarcinoma or more often mucinous non-cystic adenocarcinoma.
Benign, borderline and intraductal types grow slowly and have a good prognosis after complete surgical resection.
Widely invasive types have poor prognosis.
Intraductal papillary mucinous tumours have to be distinguished from mucinous cystic tumours which do not show any communication with the duct system and occur mainly in the tail of the pancreas of female patients.
A comparison between intraductal papillary neoplasms of the biliary tract (BT-IPMNs) and intraductal papillary mucinous neoplasms of the pancreas (P-IPMNs) reveals distinct clinical manifestations and outcomes.
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