Morphological lesions of the pancreatic ducts. Significance of pyloric gland metaplasia in carcinogenesis of exocrine and endocrine pancreas.

Morphological lesions of the pancreatic ducts were studied in 113 control autopsy cases, and 84 cases of primary pancreatic carcinoma. The lesions were classified into pyloric gland metaplasia, focal pseudo-proliferation, goblet cell metaplasia, squamous metaplasia, and atypical proliferation. Diabetes mellitus or glycosuria, alcohol intake, and smoking do not seem to have any close associations with these lesions or pancreatic carcinoma. Pyloric-gland and squamous metaplasias were found at nearly comparable incidences both in control and carcinoma cases, but marked atypical proliferations, which were indistinguishable from carcinoma in situ or intraductal spreading of carcinoma, were more frequently observed in the carcinoma cases. Pyloric gland metaplasia was the most common among the various lesions, and considered to represent nonspecific change of the pancreatic duct. However, it was suggested that some of the metaplastic lesions might be transformed into atypical proliferations and further into carcinoma in situ. The expected latent period from the appearance of in situ lesion to overt pancreatic carcinoma may be a clue to early diagnosis and effective surgical treatment, but possible multiplicity of carcinoma in situ or intraductal spreading of carcinoma even at its early stage will burden further problems on its treatment. On rare occasions, argyrophil cells were found in the pyloric gland metaplasia, and its significance was discussed in relation to the genesis of Zollinger-Ellison tumor.