The DNA of tumor cells is characterized by a combination of mutations: translocations, base pair exchanges and different sets of chromosomes. Of crucial importance is the question which mutations are of growth-determining importance for carcinogenesis.
The majority of detectable changes in the DNA code are so-called "passenger mutations". They arise in the course of the many cell divisions of a clone, but are not crucial for the survival and uninhibited proliferation of the cells. Crucial for this are the so-called "driver mutations" also known as drivers. These aberrations of the DNA give the tumour clone the decisive growth advantage over normal cells. So far, > 500 mutated key genes (oncogenes) have been discovered for individual tumours, which is about 2.5% of all protein-coding genes.