The development of cancer is a complex process. Between the development of the individual cancer cell and the occurrence of a detectable cancer disease can happen in several years. Tumors can have different causes, but they always have a degenerate cell with a defective genome.
The causes of a tumor can be accidental, but also accumulated DNA damage due to risky behavior such as smoking. Because the starting point of a cancer is the genome. The genes, the carriers of the hereditary cause damage that can no longer be repaired. Three groups of genes play a role as the cause of tumors: the oncogenes, the suppressor genes and the repair genes.