The following information may help to address your question:
In general, cancers are caused when the genes that regulate the cell's growth and division are changed. The cause of the changes is unknown, but may be due to a combination of genetic factors, environmental factors, and the process of aging. The development of cancer is not a quick or simple process. It is a progression involving a build-up of changes in a number of different genes in the cells of the body tissues over time.