The sources of heritable variation in cellular growth capacities.

Diverse genetic and epigenetic changes occur in cells in response to unfavorable environments. Most of these changes do not directly cause the malignant transformation. An occasional, rare change can lead to cancer, although it may be expressed only in the environmental context that gave rise to it. The variety of such changes is so enormous that it is impossible to derive unique, cellular mechanisms. A set of rules is derived for describing the interactions between cell and its surround which result in malignancy. It has often been said that 'nature is simple'--illusion! It is our mind which looks for simplicity to avoid effort. L. Brillouin, Scientific Uncertainty and Information 1964.