Early lesions during pancreatic carcinogenesis induced in the Syrian hamster by DHPN or DOPN. II. Ultrastructural findings.

The ultrastructure of multi-locular cystic lesions and atypical epithelial proliferations arising in the Syrian hamster pancreas prior to the appearance of carcinomas during treatment with the related carcinogens di-hydroxy-di-n-propyl nitrosamine and di-oxo-di-n-propyl nitrosamine was compared in order to assess the role these lesions play in tumourigenesis in this model. Whereas the cells of low cuboidal ductular morphology forming multi-locular cystic lesions demonstrated basic fine structural similarities to normal ductular epithelium the columnar cells prevalent in atypical epithelial proliferations exhibited marked alterations reminiscent of ultrastructural features present in many cells of carcinomas. Most conspicuous amongst these changes were production of mucous granules and occurrence of goblet type cells, glycogen accumulation, nuclear abnormalities and thickening and interruption of the basement membrane. The ultrastructural findings support the view that the atypical proliferations showing alteration in carbohydrate metabolism are precursors for pancreatic carcinomas in the Syrian hamster.