[Morphological manifestations of tumor progression]

The paper reviews the theory of Foulds on the tumor progression and necessitates a wider application and study of this theory. The biological basis of the tumor progression consists in variability and heterogeneity of the tumor cells undergoing tissue selection resulting in the appearance of tumor cells with new properties. Morphological manifestations of the tumor progression subdivided into 4 groups are considered. Some aspects of application of the theory to histological diagnosis of tumors and its significance in treatment of cancer are described. It is emphasized that the theses of the tumor progression theory are essential for the development of basic research in oncology.