Newer concepts of cancer of the colon and rectum: Similarities between human and experimentally induced tumors of the large intestine

Summary Several points of similarity between human colorectal adenomatous polyps and those induced in rats have been discussed. Morphologically and in distribution, the polyps and carcinomas bore a resemblance to the point of being nearly indistinguishable. One point in deviation was the absence of metastases. Different methods of dosing have altered the frequency of occurrence of the tumors and, in the case of oophorectomy, the distribution. The variations may well be relevant to the epidemiologic differences in human colonic tumors, in relation to diet and exposure to possible carcinogenic agents, for example. Evan though similarities exist, implications as to etiology are not intended. It is felt that experimental methods may contribute to our understanding of colorectal adenomatous polyps and carcinomas.