STUDIES ON CARCINOGENESIS AND EXTENSION OF 1, 2-DIMETHYLHYDRAZINE INDUCED LARGE-BOWEL CANCER IN RATS

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Studies on carcinogenesis and extension of 1, 2-dimethylhydrazine (DMH) induced large-bowel cancer were carried out in 40 rats using a complete autopsy at 220 days from the start of the treatment.The histological changes of the colon treated with DMH were divided into 4 lesions by serial sectioning of the entire colons: 1) atypical glands, 2) adenoma, 3) non-invasive cancer, and 4) invasive cancer.As many as 86% of colonic adenocarcinomas were originated as de novo cancer, and theremaining 14% arose from adenoma. Carcinogenesis of this model showed higher incidence in theleft half of the colon, and a tendency of multiplicity.Histological studies revealed well differentiated adenocarcinoma, poorly differentiatedadenocarcinoma and mucinous carcinoma, with high incidence of peritoneal dissemination andabdominal lymphnode metastasis.