You don't need breasts, so how come a tumor in there somehow takes away your life? The answer lies in understanding the biology of a tumor.
A tumor is the gathering of abnormal cells. Normally, cells divide and reproduce when needed and stop dividing when no longer necessary. Think about a cut on your skin - the cells divide and reproduce to create new skin, then stop when everything is back as it should be.
Cancer cells are abnormal because they don't stop dividing and reproducing, and when they group together, a tumor is formed. It's like that cut on your finger - if the cells didn't stop, you would end up with a growing lump instead of smooth skin.
The cancer cells can also spread to other parts of the body and form tumors there. The reason these tumors kill is because they interfere with the body's ability to function. Blood goes to the tumor instead of other parts of the body where it is needed. If it is in a major organ, it then interferes with the way that organ functions. So, even after surgery, chemotherapy, and radiation, if just one cancer cell remains, that one cell can lead to tumors in other parts of the body and that is what ends up causing the death of survivors.
This is a very simplistic answer, but it's the easiest one to give. Hope that helps!
Written by April Sampson