Neoplasms may be the result of the reestablishment of a phylogenetically primitive line of cells rather than the direct result of cell alteration by environmental factors. Cells with primitive potential are continually appearing in the ordinary process of tissue repair, but these cells are destroyed by an intact immunosurveillance system. Any agent which promotes prolonged cell proliferation, or depresses the immunosurveillance system, causes the production of proportionately larger numbers of these regressive cells which overwhelm the immunological protective mechanism. Since these cells possess more primitive enzymatic and metabolic processes, they may become established as unequal competitors in a common nutritional system.
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