Ultrastructural analysis of pancreatic carcinogenesis: morphological characterization of N-nitroso-bis(2-hydroxypropyl)amine-induced neoplasms in the Syrian hamster.

Tumours of the exocrine pancreas of the Syrian hamster, induced by lifetime weekly injections of N-nitroso-bis-(2-hydroxypropyl)amine(BHP), were studied by light and electron microscopy and their fine structure was characterized. The neoplasms were cystic and papillary adenomata and adenocarcinomata, whose development was preceded by that of cystic foci of flattened epithelial cells. The tumour epithelia consisted of flattened, cuboidal or columnar cells, the latter frequently showing mucous metaplasia. Although there was a considerable degree of ultrastructural pleomorphism within tumours, some of which was apparently related to maturation, all the neoplasms shared sufficient common cellular characteristics to indicate a common histogenesis. Although the neoplasms induced by BHP closely resembled human "ductal" pancreatic tumours, they did not appear to arise from the ducts.