Primary target for carcinogens are determinants of cellular membranes, but not cell's DNA. On the first stage of carcinogenesis (initiation) two normal somatic cells of one organ or tissue may create dikaryons, but in some cases nonviable polykaryocytes. During the perforation of cellular membranes induced by different carcinogenic agents and factors, the total negative charge of plasma membranes decrease and the cells acquire the capability of closely approaching (adhesion), which frequently, especially upon coincidence of the perforated parts, may serve as a prerequisite to fusion process. After synchronous mitosis or simple mechanical assembly of hetero-or homokaryons nuclei, mononuclear hybrid precancerous cells develop, with a tetraploid set of chromosomes on initial stage of hybridization. In addition to the data evidencing the hybrid origin of a cancer cell, this work attempts to answer some important and still unanswered questions of modern oncology.