[Dynamics and the staging of the histological changes in the liver in experimental diethylnitrosamine carcinogenesis]

A histologic study was carried out on the liver of rats treated each with 130 mg per kg body mass of diethylnitrosamine introduced intraperitoneally once in a week, over a period of 9 weeks. After the examination the experiment lasted further 17 weeks. A description is given of the histopathologic findings in the course of the experiment. Although some great diversity was found the setting in of the lesions showed a step-like character, which to a certain extent spoke of four definite stages in the development of the diethylnitrosamine chronic intoxication and cancerogenesis. The first stage, called alterative, included the period up to the 21st day of the experiment and was characterized by moderate dystrophic and inflammatory changes. The second stage, an alterative and proliferative one, included the time period from the fourth up to the eighth week and was distinguished by severe dystrophic, inflammatory, and proliferative processes. The third stage, called proliferative and tumorigenic, lasted from the ninth up to the seventeenth week and was shown to be the period of necrosis, cholangiofibrosis, and the production of neoplastic nodes. The fourth stage was the one of malignant growth, and it was dominated by the development of various, most often hepatocellular carcinomas that were seen after the seventeenth week of the experiment. All data referred to the use of nitrosamines and their transient compounds as pathogenic ecologic factors both for humans and animals, and is discussed in view of the opportunities for prophylaxis and therapy that are disclosed by knowing the dynamics of the particular pathologic process.