Cancer is a group of many diseases that share similarities and can occur anywhere in the body. What these diseases have in common is that they are the result of genetic changes within our genes.

These changes disrupt the ways our cells function and alter the systems that manage and control our cells’ lifecycle. These genetic changes result in unrestricted cell growth and stop our cells from going through their normal death process.

Before we understand how this happens, it's important to understand our bodies are growing new cells all the time, how this process works, the role of stem cells, and what DNA is and how it fits into this process

To make new cells our existing cells divide and multiply, copying themselves and passing on their exact sequence of DNA. Occasionally things go wrong in this process because of damage that has been done to our DNA. Our DNA can be damaged by radiation (the sun or cancer treatment), chemicals in the atmosphere, oxygen radicals, cosmic rays (which are small waves that come from space), but the key issue is that somehow our DNA has been physically damaged.

Dividing breast cancer cell.

Source: National Cancer Institute & University of Pittsburgh