Most cancer researchers are based on a "multi-step model of carcinogenesis. The multi-step cancer development model attempts to understand the cause. The proliferation of the relevant genetically modified cell into a clump of cells, without external influences over time, or faster by doctoral students influences increased, thereby significantly the probability of another relevant genetic changes under the multi-step process. Such changes can again be induced by external factors (carcinogenic substances), or come by genetic instability of the altered cell population reached. Irritating stimuli can increase the proliferation speed up this process. Up to ten different mutations have to be done. Some of these necessary mutations can be inherited, which explains why even very young children can get cancer and that cancer can occur in so-called "cancer family" frequently. A typical example is the hereditary xeroderma pigmentosum. In close relatives of patients with breast cancer is likely to get breast cancer twice as high as in the general population. In the intermediate steps of tumor development (promotion and progression) is not genotoxic processes play a major role, which could tempt observers to these influences than actual "carcinogen" classification. The actual malignancy (malignant tumors) of the degenerated cell in the phase of progression achieved. The terms promotion and progression are increasingly being replaced by the concept of co-carcinogenesis.
The older so-called "three-step model" breaks down the cancer, however in phases: initiation, promotion and progression. Asked that the years or decades of latency period between the initial DNA damage So the transformation of a single cell, and the detectable tumor are explained. The problem with the three-stage model is that the terms describe initiation, promotion and progression and not only explain the cause.
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