Early changes in the experimentally produced adenomas and adenocarcinomas of the stomach.

Until the work of Stewart and Lorenz in 1942 (7), attempts at producing adenocarcinomas of the stomach by means of the carcinogens had failed. Klein and Palmer reviewed these efforts in 1941 (3). Carcinogens had been administered with the diet mixed with roughage, placed in the mouth by dropper and kept within the lumen of the stomach for some time by means of paraffin pellets. Squamous-cell carcinomas were produced in the lower end of the esophagus and in the forestomach of rats and mice, but not adenocarcinomas of the glandular portion. The forestomach is lined with squamous cell epithelium and theoretically is not protected by mucin as is the rest of the stomach. Stewart (6) placed the carcinogen within the wall of the stomach of mice by means of threads, oil, and horse serum. The greatest production of adenocarcinomas was obtained with a suspension of methylcholanthrene in horse serum. Of 47 mice injected with this suspension, 6 developed adenocarcinomas; 12, mixed adenocarcinomas and sarcomas; 6, adenocanthomas; 2, mixed adenocanthomas and sarcomas; 7, adenomas; and 3, sarcomas. The lesions were produced within 19 to 46 weeks. In this investigation, threads impregnated with methylcholanthrene were used to produce adenocarcinomas and adenomas, and the early changes occurring about them were studied in an attempt to disclose the mechanism of formation of new growths in the stomach. The reactions of the cells of the stomach wall to unimpregnated threads and to threads containing a similar but noncarcinogenic anthracene compound were also studied in order to distinguish unusual changes about the threads con-