[Morphology of gastrointestinal tract tumors induced in rats by N'-nitro-N-nitrosoguanidine].

For 14 months 200 white noninbred male rats received N-methyl-N'-nitro-N-nitrosoguanidine in various concentrations in drinking water. The animals were sacrificed in 18--22 months. Out of 178 rats surviving the time of appearance of the first tumor 64 animals developed tumours of the gastrointestinal tract. Histologically, gastric tumours in 34 cases were presented by adenomatous outgrowths, in 11 the changes were extremely suspect of cancer, in 2 cases morphologically true cancer was observed. The induced gastric tumours had certain peculiarities as compared with the corresponding tumours of man which consisted in tumour cells growing through the thickness of the wall without marked atypism and lack of metastases. Intestinal tumours were sarcomas in which simultaneously some mesenchymal components were present.