In age groups from 20 to 60 years old, proliferation and differentiation of cells happen in a morphofunctional zone, in the electric field excited by 12 pairs of mother and daughter cells, turned out at cambial cells division. Thus in daughter cells the Src SH2 domain necessary both for cytoskeleton formation and tyrosinase activization is activated. If the conditions for strengthening of tyrosinase activity are created in organism, the portion of Src participating in the cytoskeleton building can decrease to critical level that will lead to development of a malignant tumor. If action of a stimulating factor is quite strong, proliferation of malignant cells begins at a stage of melanocyte, and a melanoma occurs. If action of factors is long and not strong, more remote descendants of daughter cells proliferate, and a cancer appears. In order that there will be a normal differentiation of malignantly changed daughter cells, it is necessary to block the tyrosinase. Thus all SH2 domains will go on cell cytoskeleton formation.