How Does Cancer Develop?
Cancer is caused by certain changes to genes, the basic physical units of inheritance. Genes are arranged in long strands of tightly packed DNA called chromosomes.
Credit: Terese Winslow
Cancer is a genetic diseaseÃ¢â‚¬â€that is, it is caused by changes to genes that control the way our cells function, especially how they grow and divide.
Genetic changes that cause cancer can happen because:
of errors that occur as cells divide.
of damage to DNA caused by harmful substances in the environment, such as the chemicals in tobacco smoke and ultraviolet rays from the sun. (Our Cancer Causes and Prevention section has more information.)
they were inherited from our parents.
The body normally eliminates cells with damaged DNA before they turn cancerous. But the bodyÃ¢â‚¬â„¢s ability to do so goes down as we age. This is part of the reason why there is a higher risk of cancer later in life.
Each personÃ¢â‚¬â„¢s cancer has a unique combination of genetic changes. As cancer continues to grow, additional changes will occur. Even within the same tumor, different cells may have different genetic changes.