Objective: To assess of the grade of malignancy of intraductal papillary neoplasm of the pancreas (IPNP). Design: Retrospective analysis. Setting: University hospital, Japan. Patients: 8 men and 9 women, mean age 67 years, with IPNP. Results: 12 lesions were in the head of the pancreas, two in the body and three in the tail. There were no differences in the age and sex of the patients, the presence of diabetes mellitus or history of pancreatitis, serum concentrations of carcinoembryonic antigen, and CA 19-9, pancreatic function test, and the site of origin of benign and malignant IPNP. The mean diameter of the main pancreatic duct was 16 mm in the four malignant tumours, but 6 mm in the 13 benign IPNP (p < 0.05). 10 of the 13 benign IPNP were located in the branch duct, two in the main pancreatic duct, and another in both the main and branch ducts, while all four malignant IPNP were situated in the main duct (p < 0.01). Mural nodules were detectable preoperatively in all four malignant IPNP but in only 5 of the 13 benign tumours (39%). The mean diameter of the mural nodules in the five benign IPNPs was 3mm, whereas that in the four malignant ones was 24 mm (p < 0.01). All but one patient (who had a malignant IPNP) were alive for one to 36 months (mean 16 months) after resection. Conclusions: IPNP is a unique variant of pancreatic exocrine neoplasm with a good prognosis after resection. The diameter of the main pancreatic duct, size of the mural nodule, and site of the tumour (main pancreatic duct or branch duct) differ significantly between benign and malignant tumours.
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