[Pathobiology of carcinogenesis and the growth of neoplasms].

The importance of carcinogenicity by chemical substances is reviewed with regard to the increasing number of human neoplasms (1955: 39703; 1972: 62556) in the German Democratic Republic. The organotropic action of some carcinogens, the transplacental tumour induction, the endogenous formation of oncogenic N-nitroso compounds from inactive precursors in the stomach of experimental animals, and the role of carcinogens derived from plants are analysed. Up to now it remains uncertain, whether DNA and RNA viruses responsible for tumour development in different species of animals may effect tumour growth in human beings as well.