Abstract
Donryu rats were given N-methyl-N'-nitroN-nitrosoguanidine per os for a maximum period of 14 months, and sacrificed at intervals in order to assess histopathologic process occurring in the glandular stomach. A total of 129 gross lesions were found in 72 of 85 effective animals, which histologically included 48 adenomatous hyperplasias secondary to regenerative hyperplasias of glands at the margins of erosions or shtsllow ulcers, 21 adenocarcinomas and 2 sarcomas. All except one (intramucosal mucous cell carcinoma) of the 21 adenocarcinomas developed on the basis of adenomatous hyperplasias, and three patterns were discriminated in the studies. In Series A adenomatous tissues proliferated horizontally and then invaded submucosa or below in a ciasson-like fashion; malignant change took place at the deepest portion of such a lesion and ultimately led to adenocarcinoma that resembled Borrmann III human gastric cancer. In Series B adenomatous tissues grew upwards to form a polypoid mass, which underwent malignant change and resulted in a Borrmann I type adenocarcinoma. In Series C which appeared to be the commonest pattern, adenomatous tissues grew downwards through small interruption of muscularis mucosae; adenocarcinoma developed at the bottom of such an iceberg-like lesion and eventually formed a Borrmann II type tumor as a result of secondary ulceration.
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