Replying to @Candice J. Gossett 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. Cancer is a genetic disease—that is, it is caused by changes to genes that control the way our cells function, especially how they grow and divide. The main reasons are genetics and certain environmental or behavioral triggers. The tendency to develop some types of cancer is believed to be inherited — t