Cancer is a genetic disease that is, cancer is caused by certain changes to genes that control the way our cells function, especially how they grow and divide. These changes include mutations in the DNA that makes up our genes Genetic changes that increase cancer risk can be inherited from our parents if the changes are present in germ cells, which are the reproductive cells of the body (eggs and sperm). In general, cancer cells have more genetic changes than normal cells. But each person’s cancer has a unique combination of genetic alterations. Some of these changes may be the result of cancer, rather than the cause. As the cancer continues to grow, additional changes will occur. Even within the same tumor, cancer cells may have different genetic changes.