Abstract
Serial studies by endoscopy and biopsy were made in a Beagle dog during and after oral administration of N-methyl-N'-nitro-N-nitroguanidine (MNNG). Between the 23rd and the 45th week of observation erosions and ulcers appeared at the angulus of the stomach and turned into ulcer scar. A depression with atypical glands was seen in the ulcer scar of the posterior wall of the angulus at the 94th week. It developed elevated margins at the 102nd week, when a well differentiated adenocarcinoma was found histopathologically. Ulceration and reepithelialization were observed in the early carcinoma. The carcinoma progressed into a larger one of Borrmann's type 2 at the 115th week and further into its type 3 at the 181st week. A second carcinoma with signet ring cell carcinoma developed in the anterior wall of the angulus. The two carcinomas fused and formed a single lesion. At autopsy in the 216th week the carcinoma invaded the serosa, and metastasis to regional lymph nodes was observed.